Physics Flashcards
1
Q
Centripetal Force (F)
A
= m (v^2 / r)
Points radially inward
2
Q
Centripetal Acceleration (a)
A
= v^2 / r
3
Q
SI Units
A
Meter, Kilogram, Second, Ampere, Mole, Kelvin and Candela
4
Q
Vector
A
Have magnitude and direction
5
Q
Is displacement vector or scalar?
A
Vector
6
Q
Is velocity vector or scalar?
A
Vector
7
Q
Is acceleration vector or scalar?
A
Vector
8
Q
Is force vector or scalar?
A
Vector
9
Q
Scalar
A
Have magnitude but no direction or dimension
10
Q
Is speed vector or scalar?
A
Scalar
11
Q
Are coefficients of friction vector or scalar?
A
Scalar
12
Q
Dot product
A
Multiplying 2 vectors and resulting in a scalar quantity
= |A| |B| cos (theta)
13
Q
Cross product
A
Multiplying 2 vectors and resulting in a vector quantity
= |A| |B| sin (theta)
14
Q
Static friction (fs)
A
= 0 < fs < fk
Exists between 2 objects that are not in motion relative to one another
Can take on many values depending on the magnitude of an applied force
15
Q
Kinetic friction (fk)
A
= us N
Exists between 2 objects that are in motion relative to one another
A constant value
16
Q
Coefficient of friction
A
Depends on the 2 materials in contact
17
Q
Which is greater: the coefficient of static friction or the coefficient of kinetic friction?
A
The coefficient of static friction
18
Q
Newton’s first law (the law of inertia)
A
F = m a = 0
An object will remain at rest or move with constant velocity if there is no net force acting on it
19
Q
Newton’s second law
A
F = m a
Any acceleration is the result of the sum of the forces acting on an object
20
Q
Newton’s third law
A
Any 2 objects interacting with one another experience equal and opposite forces as a result of their interaction
21
Q
Is free fall linear, projectile or circular motion?
A
Linear
22
Q
Linear motion
A
Motion in which the velocity and acceleration are parallel or antiparallel
23
Q
Projectile motion
A
Contains x and y components
The only force acting on the object is gravity
24
Q
Inclined planes
A
Two dimensional motion
Dimensions are parallel and perpendicular to the surface of the plane
25
What are the dimensions of circular motion?
Has radial and tangential dimensions
26
Uniform circular motion
The only force is the centripetal force
No work is done
Potential energy is constant
27
In which direction does instantaneous velocity point?
Always points tangentially
28
Translational equilibrium
Occurs in the absence of any new forces acting on an object
| The object has constant velocity and/or rotational equilibrium
29
Rotational equilibrium
Occurs in the absence of any new torques acting on an object
| The object has constant angular velocity
30
Component vectors
```
x = v cos (theta)
y = v sin (theta)
```
31
Velocity (v)
= x / t
32
Universal gravitation equation (F)
= (G m1 m2) / r^2
33
Acceleration (a)
= v / t
34
Kinematics (no displacement)
v = vo + (a t)
35
Kinematics (no final velocity)
x = (vo t) + [(a t^2) / 2]
36
Kinematics (no time)
v^2 = vo^2 + (2 a x)
37
Kinematics (no acceleration)
x = v t
38
Components of gravity on an inclined place
Fg, parallel = m g sin (theta)
| Fg, perpendicular = m g cos (theta)
39
Torque (T)
= r F sin (theta)
40
Examples of potential energy
Gravitational, electrical, elastic, chemical
41
Gravitational potential energy (U)
= m g h
42
Conservative forces
The mechanical energy of the system remains constant
| The path the object takes does not matter
43
Nonconservative forces
The mechanical energy of the system decreases (energy is dissipated)
The path the object takes matters (more energy is dissipated with a longer path)
44
Is gravity a conservative or nonconservative force?
Conservative
45
Are electrostatic forces conservative or nonconservative forces?
Conservative
46
Are elastic forces conservative or nonconservative forces?
Conservative
47
Is friction a conservative or nonconservative force?
Nonconservative
48
Is air resistance a conservative or nonconservative force?
Nonconservative
49
Is viscous drag a conservative or nonconservative force?
Nonconservative
50
Work (W)
= F d cos (theta)
= P delta V
= delta K
= delta U = q delta V
51
The dot product of the force and displacement vectors
W = F d cos (theta)
| mechanical work
52
The area under a pressure-volume curve
W = P delta V
| isobaric gas-piston system
53
The work-energy theorem
W = delta K
54
As the length of an inclined plane increases, what happens to the force required to move an object the same displacement?
As the length of an inclined plane increases, the amount of force necessary to perform the same amount of work (moving the object the same displacement) decreases.
55
As the effort decreases in a pulley system, what happens to the effort distance to maintain the same work output?
As the effort (required force) decreases in a pulley system, the effort distance increases to generate the same amount of work
56
What accounts for the difference between work input and work output in a system that operates at less than 100% efficiency?
The decrease in work output is due to nonconservative or external forces that generate or dissipate energy
57
What does it mean for a device to provide mechanical advantage?
When a device provides mechanical advantage, it decreases the input force required to generate a particular output force. Generally, this is accomplished at the expense of increased distance over which the force must act.
58
Total mechanical energy
= U + K
| The sum of a system's kinetic and potential energies
59
What happens if only conservative forces are acting on an object?
The total mechanical energy is conserved
60
Kinetic energy (K)
= 1/2 m v^2
61
Elastic potential energy (U)
= 1/2 k x^2
62
Conservation of mechanical energy (delta E)
= delta U + delta K = 0
63
Work done by nonconservative forces (W)
= delta E = delta U + delta K
64
Power (P)
= W / t = delta E / t
65
Mechanical advantage
= F out / F in
66
Efficiency
= W out / W in
| = [(load) (load distance)] / [(effort) (effort distance)]
67
Why is there no work done in uniform circular motion?
The displacement vector and force vector are always perpendicular to one another; therefore, no work is done.
68
Why is potential energy constant in uniform circular motion?
The potential energy does not depend on the position of the object around the circle.
69
The zeroth law of thermodynamics
When two objects are both in thermal equilibrium with a third object, they are in thermal equilibrium with one another
No heat is flowing
70
Closed system
Transfers energy
| Does not transfer matter
71
Isolated system
Does not transfer energy or matter
72
Open system
Transfers both energy and matter
73
State function
Variables independent of the path taken to achieve a particular equilibrium and are properties of a given system at equilibrium
They may be dependent on one another
74
Process function
Define the path (or how the system got to its state) through variables
75
Is heat a process or state function?
Process
76
Is work a process or state function?
Process
77
Is pressure a process or state function?
State
78
Is density a process or state function?
State
79
Is temperature a process or state function?
State
80
Is volume a process or state function?
State
81
Is enthalpy a process or state function?
State
82
Is internal energy a process or state function?
State
83
Is Gibbs free energy a process or state function?
State
84
Is entropy a process or state function?
State
85
The first law of thermodynamics (conservation of energy)
U = Q - W
In a closed system, the internal energy of a system is equal to the heat put into the system minus the work done by the system
86
Conduction
Heat exchange by direct molecular interactions
87
Convection
Heat exchange by fluid movement
88
Radiation
Heat exchange by electromagnetic waves
| Does not depend on matter
89
What is entropy on a macroscopic level?
The tendency towards disorder
90
What is entropy statistically?
The measure of the spontaneous dispersal of energy at a specific temperature, increasing the number of available micro states for a given molecule
91
What is a system's entropy's relationship with the system's surrounding for any thermodynamic process?
The entropy of the system and its surroundings will never decrease; it will always either remain zero or increase.
92
Specific heat
Heat required to bring the liquid to its boiling point
The amount of energy necessary to raise one gram of substance by one degree Celsius or one kelvin
93
The specific heat of water
= 1 cal / (g K)
94
Heat of transformation
During phase change, heat energy causes changes in the particles' potential energy and energy distribution (entropy), but not kinetic energy
There is no change in temperature
95
Isothermal processes
The temperature is constant, and the change in internal energy is therefore 0
96
Adiabatic processes
No heat is exchanged (Q = 0)
97
Isobaric processes
Pressure is held constant
98
Isovolumetric (isochoric) processes
The volume is held constant and the work done by or on the system is 0
99
The second law of thermodynamics
delta S universe = delta S system + delta S surroundings > 0
| In a closed system, energy will spontaneously and irreversibly go from being localized to being spread out (dispersed)
100
Entropy
A measure of how much energy has spread out or how spread out energy has become
101
Natural process
Irreversible process
| Can only be reversible under highly controlled conditions
102
Fahrenheit (F)
= 9/5 C + 32
103
Kelvin (K)
= C + 273
104
Thermal expansion equation (delta L)
= alpha L delta T
105
Volume expansion equation (delta V)
= beta V delta T
106
Heat gained or lost (with temperature change) (q)
= m c delta T
107
Heat gained or lost (phase change) (q)
= m L
108
Entropy and heat (delta S)
= Q / T
109
Why does the internal energy increase in an adiabatic compression process?
```
Q = 0
Compression = work is done on the gas (not by the gas)
Therefore, work done by the gas < 0
U = Q - W
U = 0 - (- W)
U = + W
```
110
Heat of fusion
Heat required to melt a solid
111
Heat of vaporization
Heat required to boil a liquid
112
How does gauge pressure (P gauge) relate to the pressure exerted by a column of fluid?
Gauge pressure = pressure exerted by a column of fluid + the ambient pressure above the fluid - atmospheric pressure
= P absolute (hydrostatic) - P atmospheric = (Po + p g z) - P atmospheric
113
Weight of a volume of fluid (Fg)
= density * volume * acceleration due to gravity
| = p V g
114
SI unit for pressure
Pascals (Pa)
115
Is density a scalar quantity?
Yes
116
When does gauge pressure = fluid pressure?
When the only pressure above the fluid column is atmospheric pressure
117
Pressure units
mmHg, torr, atm and Pa
118
Cohesion
Molecules attaching to one another in a fluid
| Give rise to surface tension
119
Adhesion
Molecules attaching to the container surface containing a fluid
120
What would the meniscus of a liquid that experiences equal cohesive and adhesive forces look like?
There would be no meniscus and the liquid surface would be flat
121
A block is fully submerged 3 inches below the surface of a fluid, but is not experiencing any acceleration. What can be said about displaced volume of fluid and the buoyant force?
Displaced volume = volume of the block
Buoyant force = weight of block = weight of fluid displaced
The block and the fluid in which it is immersed must have the same density
122
To determine the volume of an object by fluid displacement, must the object have a specific gravity greater than 1?
No
A fluid with a low specific gravity can be used instead of water to determine volumes of objects that would otherwise float in water
123
To which side of a hydraulic lift would the operator usually apply a force: the side with the larger cross-sectional area, to the side with the smaller cross-sectional area?
Smaller cross-sectional area. Because the pressure is the same on both sides of the lift, a smaller force can be applied on the smaller surface area to generate the desired pressure
124
Dynamic pressure
= 1/2 p v^2
Pressure associated with flow
(like kinetic energy)
125
Static pressure
Pressure associated with position
| like potential energy
126
Pitot tube
A device that measures static pressure during flow to calculate speed
127
Viscosity
How thick a fluid is (i.e. the resistance of a fluid to flow)
A measure of the fluid's internal friction
128
Laminar flow
Flow in which there are no eddies and in which streamlines roughly parallel each other
129
Turbulence
The presence of back flow or current eddies
130
How do the following concepts relate to one another: Venturi effect, Bernoulli's equation and continuity equation?
Venturi's effect results from combining Bernoulli's equation and the continuity equation
131
What variables does flow rate depend on?
Radius of the tube, pressure gradient, viscosity and length of the tube
132
What does the continuity equation describe?
The relationship of flow and cross-sectional area in a tube
133
What does Bernoulli's equation describe?
The relationship between height, pressure and flow
134
What does the Venturi effect describe?
The direct relationship between cross-sectional area and pressure
135
Can the continuity equation be applied to human circulation?
No, due to the presence of pulses, the elasticity of the vessels and the nature of the pressure gradient
Poiseuille's law can be used for isolated segments
136
During exhalation, how does the total resistance of the encountered airways change as air leaves the alveoli to escape the nose and mouth?
Total resistance increases as the air exits the body despite the increase in the diameter of the airways. This is because there are fewer airways in parallel with each other.
137
How does flow in the venae cavae relate to flow in the main pulmonary artery?
In theory, there should be equal flow in the venae cavae and the main pulmonary trunk. In reality, the flow in the venae cavae is actually slightly less than that in the pulmonary trunk because some of the blood entering the right side of the heart is actually from cardiac (coronary) circulation, not systemic circulation.
138
Density (p)
= m / V
139
Specific gravity (SG)
= p / (1 g/cm^3)
140
Pressure (P)
= F / A
141
Absolute (hydrostatic) pressure (P)
= Po + p g z
= Pressure at the surface of the fluid (usually atmospheric pressure) + pressure due to the fluid itself
The sum of all the pressures at a certain point within a fluid
142
Pascal's principle
```
P = F1 / A1 = F2 / A2
F2 = (F1 A2) / A1
```
Pressure applied to an incompressible fluid will be distributed undiminished throughout the entire volume of the fluid
143
Buoyant force (F buoyant)
= p fluid V fluid displaced g = p fluid V submerged g
144
Poiseuille's law
Q = (pi r^4 delta P) / (8 nu L)
```
Q = flow rate
r = radius of tube
P = pressure
nu = fluid viscosity
L = length of tube
```
Determines the rate of laminar flow
145
Critical speed (vc)
= (Nr nu) / (p D)
```
Nr = Reynold's number
nu = fluid viscosity
p = fluid density
D = diameter of tube = 2 r, r = radius of tube
```
146
Continuity equation (Q)
= v1 A1 = v2 A2
| Similar to conservation of mass
147
Bernoulli's equation
P1 + 1/2 p v1^2 + p g h1 = P2 + 1/2 p v2^2 + p g h2
(Similar to conservation of energy)
States that the sum of static pressure and dynamic pressure will be constant between any two points in a closed system
148
Can fluids exert perpendicular forces?
Yes
149
Can fluids exert shear forces?
No
150
Is pressure a scalar or vector quantity?
Scalar
151
In which direction does a gas exert pressure on a container?
Perpendicular direction
152
Hydraulic machines
Operate based on the application of Pascal's principle to generate mechanical advantage
153
Archimedes' principle
Governs the buoyant force
When an object is placed in a fluid, the fluid generates a buoyant force against the object that is equal to the weight of the fluid displaced by the object
154
In which direction does the buoyant force point?
Opposite to the direction of gravity
155
What happens if the maximum buoyant force is larger than the force of gravity on the object?
The object will float (only works if the object is less dense than the fluid)
156
What happens if the maximum buoyant force is smaller than the force of gravity on the object?
The object will sink (only works if the object is more dense than the fluid)
157
Viscous drag
Nonconservative force generated by viscosity
158
When will there be an inverse relationship between pressure and speed (Venturi effect)?
Horizontal flow
159
When will there be a direct relationship between cross-sectional area and pressure exerted on the walls of the tube (Venturi effect)?
In a closed system
160
Venturi effect
In horizontal flow, there will be an inverse relationship between pressure and speed
In a closed system, there will be a direct relationship between cross-sectional area and the pressure exerted on the walls of the tube
161
Is the circulatory system open, closed or isolated?
Closed
162
Does the circulatory system have constant flow?
No
163
What happens to resistance as the cross-sectional area increases?
Decreases
164
What motivates arterial circulation?
The heart
165
Does venous circulation have higher or lower volume than arterial circulation?
3 times higher
166
What motivates venous circulation?
Skeletal musculature and expansion of heart
167
What creates the pressure gradient for the respiratory and circulatory systems?
Inspiration and expiration
168
What is the air speed in alveoli?
Zero
169
Why is the speed of blood in the aorta much higher than the speed of blood through a capillary bed?
The cross-sectional area of all the capillaries added together is much greater than the cross-sectional area of the aorta
170
How does Bernoulli's equation explain the upward force that permits planes to fly?
The speed of airflow is greater over the curved top of the wing, resulting in less pressure on the top of the wing and the production of a new upward force on the wind, in turn resulting in flight
171
When placed one meter apart from each other, which will experience a greater acceleration: one coulomb of electrons or one coulomb of protons?
Electrons will experience the greater acceleration because they are subject to the same force as the protons, but have a significantly smaller mass
172
Is blood a conductor or an insulator?
Conductor
173
Is hair a conductor or an insulator?
Insulator
174
Is copper a conductor or an insulator?
Conductor
175
Is glass a conductor or an insulator?
Insulator
176
Is iron a conductor or an insulator?
Conductor
177
Is sulfuric acid a conductor or an insulator?
Conductor
178
Is distilled water a conductor or an insulator?
Insulator
179
What is the electric field midway between two negative charges in isolation?
The electric field would be zero because the two charges are the same. In this cases, the fields exerted by each charge at the midpoint will cancel out and there will be no electric field.
180
What direction does a negative electrostatic force point?
Towards the source charge (because we use the perspective of a small positive test charge)
181
What direction does a positive electrostatic force point?
Away from the source charge (because we use the perspective of a small positive test charge)
182
How do distance and charge relate to electrostatic force?
Electrostatic force is directly related to the charge and related to distance by an inverse square relationship
183
How do distance and charge relate to electric field?
Electric field is unrelated to test charge but is still related to distance by an inverse square relationship
184
What creates the electric field: test charge or source charge?
Source charge
185
How does a change in electrical potential energy from -4 J to -7 J reflect on the stability of a system?
The system has become more stable
186
The relationship between electrical potential energy and Coulomb's law
Electric potential energy is Coulomb's law multiplied by distance
187
The relationship between gravitational potential energy and the universal law of gravitation
Gravitational potential energy is the universal law of gravitation multiplies by distance
188
How does electrical potential energy change between two particles as the distance between them increases?
If both particles have the same charge, the electric potential energy decreases and distance increases. If the two particles have opposite charges, then the electrical potential energy increases as distance increases.
189
Electrical potential
The ratio of a charge's electrical potential energy to the magnitude of the charge itself
190
Voltage (potential difference)
A measure of the change in electrical potential between two points, which provides an indication of the tendency towards movement of a test charge in one direction or the other
191
How will a charge that is placed at a point of zero electrical potential move relative to a source charge?
A charge will move in such a way to minimize its potential energy. Placing a charge at a point of zero electrical potential does not indicate that there is zero potential difference, so the charge may or may not move (and if it moves, it may move towards or away from the source depending on the sign of the source charge and the test charge).
192
Are the units of electrical potential energy, electrical potential, potential difference (voltage) different?
Yes, electrical potential energy is in joules, while electrical potential and potential difference (voltage) are in volts
193
Equipotential lines
The sets of points within space at which the potential difference between any two points is zero (i.e. they have the same electric potential). This is best visualized as concentric spheres surrounding a source charge.
194
Electric dipole
The separation of charge within a molecule such that there is a permanent or temporary region of equal and opposite charges at a particular distance
195
What is the voltage between two points on an equipotential line? Will this voltage cause a charge to move along the line?
There is no voltage between two points on an equipotential line, so there will be no acceleration along the line. However, there is a potential difference between different sets of equipotential lines, which can cause particles to move and accelerate.
196
Why is the electrical potential at points along the perpendicular bisector of a dipole 0?
The perpendicular bisector of an electric dipole is an equipotential plane that is perpendicular to the axis of the dipole. As such, the equation V = [(k q d) / r^2] cos (theta) is necessarily equal to 0 because cos 90 = 0
197
What is the behavior of an electric dipole when exposed to an external electric field?
A dipole will rotate within an external field such that its dipole moment aligns with the field (angle between dipole and field is 0 degrees)
198
What are the requirements to have a nonzero electric field?
Charge
199
What are the requirements to have a nonzero magnetic field?
Moving charge
200
What are the requirements to have a nonzero magnetic force?
External field acting on a charge moving in any direction except parallel or antiparallel to the external field
201
Which would experience a larger magnetic field: an object placed five meters to the left of a current carrying wire, or an object placed at the center of a circle with a radius of five meters?
The magnetic field created by the current-carrying wires is B = (uo I) / (2 pi r)
The magnetic field created by the loop of wire is B = (uo I) / (2 r)
The magnetic field at the center of the loop must be larger because the denominator in that equation does not include pi
202
Cross product right hand rule
Index in the direction of velocity
Palm in the direction of magnetic field
Thumb in the direction of force
203
What is the direction of force if velocity points up the page, magnetic field points to the left and the particle is an electron?
Into the page
204
What is the direction of force if velocity points into the page, magnetic field points out of the page and the particle is a proton?
None, sin 180 = 0
205
What is the direction of force if velocity points to the right, magnetic field points into the page and the particle is a Proton?
Up the page
206
What is the direction of force if velocity points out of the page, magnetic field points to the left and the particle is an electron?
Up the page
207
What is the direction of force if velocity points down the page, magnetic field points to the right and the particle is a neutron?
None, q = 0
208
Coulomb's law
Fe = (k q1 q2) / r^2
Give the magnitude of the electrostatic force vector between two charges
209
Electric field (E)
= Fe / q = (k Q) / r^2
The ratio of the force that is exerted on a test charge to the magnitude of that charge
210
Electric potential energy (U)
= (k Q q) / r
The amount of work required to bring the test charge from infinitely far away to a given position in the vicinity of a source charge
211
Electric potential (from electrical potential energy) (V)
= U / q
212
Electric potential (from source charge) (V)
= (k Q) / r
213
Voltage equation (delta V)
= Vb - Va = Wab / q
214
Electrical potential near a dipole (V)
= [(k q d) / r^2] cos (theta)
215
Dipole moment (p)
= q d
216
Electric field on the perpendicular bisector of a dipole (E)
= [1 / (4 pi epsilon o)] (p / r^3)
217
Torque on a dipole in an electric field (T)
= p E sin (theta)
218
Magnetic field from a straight wire (B)
= (uo I) / (2 pi r)
219
Magnetic field from a loop of wire (B)
= (uo I) / (2 r)
220
Magnetic force on a moving point charge (Fb)
= q v B sin (theta)
221
Magnetic force on a current-carrying wire (Fb)
= I L B sin (theta)
222
SI unit for charge
Coulomb
223
Charge on a proton and an electron
1.60e-19 C
224
Conductor
Allow the free and uniform passage of electrons when charged
225
Insulators
Resist movement of charge and will have localized areas of charge that do not distribute over the surface of the material
226
Where does the electrostatic force vector point?
Along the line connecting the centers of the two charges
227
Does every charge generate an electric field?
Yes
228
Can the electric field exert forces on other charges?
Yes
229
Field lines
Represent electric field vectors
Radiate outward from positive source charges
Radiate inward towards negative source charges
230
In which direction does a positive test charge move?
In the direction of field lines
231
In which direction does a negative test charge move?
In the opposite direction of field lines
232
How does the electrical potential energy of a system increase?
When two unlike charges move away from each other or when two like charges move towards each other
233
How does the electrical potential energy of a system decrease?
When two unlike charges move towards each other or when two like charges move further apart
234
Do different points in the space of an electric field surrounding a source charge have different electrical potential values?
Yes
235
Is voltage path dependent?
No
236
Is voltage a state or process function?
State
237
In which direction do positive test charges move?
High potential to low potential
238
In which direction do negative test charges move>
Low potential to high potential
239
In which direction to equipotential lines point?
Perpendicular to electric field lines
240
Is work done when a charge is moved from one equipotential line to another?
Yes, but it is independent of the pathway taken between the lines
241
Is work done when a charge moves from one point to another on the same equipotential line?
No
242
How is an electric dipole generated?
Two charges of opposite signs are separated by a fixed distance d
243
Will a dipole experience a net torque in an external electric field?
Yes, until it is aligned with the field
244
How are magnetic fields created?
Magnets and moving charges
245
SI unit for magnetic field
Tesla
246
Diamagnetic materials
Do not possess unpaired electrons and are slightly repelled by a magnet
247
Paramagnetic materials
Possess unpaired electrons and become weakly magnetic in an external magnetic field
248
Ferromagnetic materials
Possess unpaired electrons and become strongly magnetic in an external magnetic field
249
In which direction do field lines in magnets point?
From the North Pole to the South Pole
250
Magnetic fields in current-carrying wires
Concentric circles surrounding the wire
251
When do point charges undergo uniform circular motion?
In uniform magnetic fields, wherein the centripetal force is the magnetic force acing on the point charge
252
Lorentz force
The sum of the electrostatic and magnetic forces acting on a body
253
Magnetic field right hand rule
Thumb tangent to circle in direction of charge motion
| Curled fingers in direction of magnetic field
254
A dipole is placed in an electric field and is allowed to come to equilibrium. Why does the dipole experience no rotational or linear movement when the direction of the electric field is suddenly reversed?
Torque is a function of both force applied and the angle at which it is applied. A dipole placed in an electric field will experience a torque until it comes to rest oriented within the field, at which point the angle between the plane of the dipole and the electric field is 0 degrees. Once this point if reached, inverting the electric field has no impact on the dipole because it will now have an angle of 180 degrees, the sine of which is still 0. Note, however, that is is an unstable setup; any deviation in the dipole from its rest position will immediately result in torque on the dipole and force it to realign with the new field.
255
Current
The movement of positive charge through a conductive material over time from the high-potential end to the low-potential end
256
Voltage
A potential difference between two points
257
Electromotive force (emf)
The potential difference of the voltage source for a circuit, usually a battery
258
Conductivity
The reciprocal of resistance and is a measure of permissiveness to current flow
259
In a circuit, are the number of electrons entering a point and leaving that point the same?
Yes
260
Is the sum of voltage sources in a circuit always equal to the sum of voltage drops in that circuit?
No
261
Current unit
Amperes = C / s
262
Amperes
= C / s
263
Voltage unit
Volts = J / C
264
Volts
= J / C
265
Electromotive force (emf) unit
Volts = J / C
266
Conductivity unit
Siemens (S)
267
Kirchhoff's junction rule
The number of electrons (currents) entering a point and leaving that same point are the same
I into junction = I leaving junction
268
How does adding a resistor in series affect the total resistance of a circuit that has resistors in series?
Increase total resistance
269
How does adding a resistor in parallel affect the total resistance of a circuit that has resistors in series?
Decrease total resistance
270
What four physical quantities determine the resistance of resistor?
Resistivity, length, cross-sectional area and temperature
271
How does power relate to current, voltage and resistance?
P = I V = I^2 R = V^2 / R
272
Will the internal resistance of a battery lower the amount of current it can provide?
Yes
The internal resistance will lower the available voltage for the circuit. Lowering the available voltage will also lower current for any given resistance.
273
How does removing a resistor in series affect the total resistance of a circuit that has resistors in series?
Decrease total resistance
274
How does adding a resistor in series affect the total resistance of a circuit that has resistors in series?
Increase total resistance
275
Assuming the plates are attached by a conductive material, how does a capacitor behave after the voltage source has been removed from a circuit?
The capacitor discharges, proving a current in the opposite direction of the initial current
276
How does a dielectric material impact capacitance?
Increase capacitance
277
How does a dielectric material impact voltage?
Decrease voltage if the capacitor is isolated when the dielectric is introduced
Constant voltage if the capacitor is in a circuit when the dielectric is introduced because it is dictated by the voltage source
278
How does a dielectric material impact charge?
If the capacitor is isolated, the stored charge will remain constant because there is no additional source of charge
If the capacitor is in a circuit, the stored charge will increase
279
How does adding a capacitor in series affect the total capacitance of a circuit that has capacitors in series?
Decrease total capacitance
280
How does removing a capacitor in series affect the total capacitance of a circuit that has capacitors in series?
Increase total capacitance
281
How does adding a capacitor in parallel affect the total capacitance of a circuit that has capacitors in series?
Increase total capacitance
282
How does removing a capacitor in parallel affect the total capacitance of a circuit that has capacitors in series?
Decrease total capacitance
283
What physical qualities contribute to the capacitance of a capacitor?
Surface area, distance and dielectric constant
284
What does an ammeter measure?
Current
285
Where is an ammeter placed?
In series with the point of interest
286
What is the ideal resistance for an accurate ammeter reading?
0
287
What does a voltmeter measure?
Voltage drop (potential difference)
288
Where is a voltmeter placed?
Parallel with circuit element of interest
289
What is the ideal resistance for an accurate voltmeter reading?
Infinit amount
290
What does an ohmmeter measure?
Resistance
291
Where is an ohmmeter placed?
Two points in series with circuit element of interest
Inserted around a resistive element to measure resistance
Self-powered
292
What is the ideal resistance for an accurate voltmeter reading?
0
293
Should a voltmeter and an ammeter be placed in the same circuit?
They can be
| Voltmeters and ammeters are designed to have minimum impact on a circuit, thus they can be used together
294
Current (I)
= Q / delta t
295
Kirchhoff's loop rule
V source = V drop
In a closed loop, the sum of voltage sources is always equal to the sum of voltage drops
296
Resistance (R)
= (p L) / A
The opposition to the movement of electrons through a material
297
Ohm's law
V = I R
For a given resistance, the magnitude of the current through a resistor is proportional to the voltage drop across the resistor
298
Voltage and cell emf (V)
= E cell - (I r internal)
299
Electric power (P)
= IV = I^2 R = V^2 / R
300
Voltage drop across circuit elements (series)
V total = V1 + V2 + ...
301
Equivalent resistance (series)
R total = R1 + R2 + ...
302
Voltage drop across circuit elements (parallel)
V total = V1 = V2 = ...
303
Equivalent resistance (parallel)
1 / R total = (1 / R1) + (1 / R2) + ...
304
Capacitance (C)
= Q / V
305
Capacitance based on parallel plate geometry
C = epsilon o (A / d)
In parallel plate capacitors, capacitance is determined by the area of the places and the distance between the plates
306
Electric field in a capacitor (E)
= V / d
307
Potential energy of a capacitor (U)
= 1/2 CV^2
308
Capacitance with a dielectric material (C')
= k C
309
Equivalent capacitance (series)
1 / C total = (1 / C1) + (1 / C2) + ...
310
Equivalent capacitance (parallel)
C total = C1 + C2 + ...
311
Can current flow in non-conductive materials?
No
| Current only flows in conductive materials
312
Metallic conduction
Relies on uniform movement of free electrons in metallic bonds
313
Electrolytic conduction
Relies on the ion concentration of a solution
314
Insulators
Materials that do not conduct current
315
Kirchhoff's laws
Explain conservation of charge and energy
316
Resistor
Conductive martial with a moderate amount of resistance that slow down electrons without stopping them
Across each resistor in a circuit, a certain amount of power is dissipated, which is dependent on the current through the resistor and the voltage drop across the resistor
317
Capacitor
Has the ability to store and discharge electrical potential energy
318
Dielectric materials
Insulators placed between the plates of a capacitor that increase capacitance by a factor equal to the material's dielectric constant, k
319
Wave speed
The rate at which a wave transmits the energy or matter it is carrying
The product of frequency and wavelength
320
Frequency
A measure of how often a waveform passes a given point in space
Measured in Hz
321
Angular frequency
The same as frequency: a measure of how often a wave form passes a given point in space
Measured in radians per second
322
Period
The time necessary to complete a wave cycle
323
Equilibrium position
The point with zero displacement in an oscillating system
324
Amplitude
The maximal displacement of a wave from the equilibrium position
325
Traveling wave
Have nodes and antinodes that move with wave propagation
| Have continuously shifting maximum and minimum displacement
326
Standing wave
Have defined nodes and antinodes that do not move with wave propagation
327
What happens if two waves that are perfectly in phase collide?
The amplitude of the resulting wave is equal to the sum of the amplitudes of the interfering waves
328
Are sound waves transverse or longitudinal waves?
Longitudinal waves
329
How does applying a force at the natural frequency of a system change the system?
The object will resonate because the force frequency equals the natural (resonant) frequency. The amplitude of the oscillation will increase.
330
What happens if two waves that are perfectly out of phase collide?
The amplitude of the resulting wave is the difference of the amplitudes of the interfering waves
331
How is sound produced and transmitted?
Sound is produced by mechanical vibrations, generated by solid objects and fluids
Sound is propagated as longitudinal waves in matter
332
To which property of a sound wave does amplitude correspond?
Volume (sound level) = intensity
333
To which property of a sound wave does frequency correspond?
Pitch
334
If two objects are traveling towards each other, how does the apparent frequency differ from the original frequency?
It is larger
335
If two objects are traveling away from each other, how does the apparent frequency differ from the original frequency?
It is smaller
336
If one objects is following another, how does the apparent frequency differ from the original frequency?
It could be higher, lower or equal to the original frequency depending on the relative speeds of the detector and the source
337
Can sound propagate in a vacuum?
No
338
What phenomenon can be detected or treated using ultrasound?
Prenatal screening, diagnose gallstones, breast and thyroid masses, and blood clots, needle guidance in biopsy, dental cleaning, treating deep tissue injuries, kidney stones, small tumors, cataracts, etc.
339
Wavelength of a pipe open in both ends (i.e. open pipe) (lambda)
= 2 L / n
340
Wavelength of a pipe open in one end (i.e. closed pipe) (lambda)
= 4 L / n
341
Wavelength of a pipe closed on both ends (i.e. string) (lambda)
= 2L / n
342
Wave speed equation (v)
= frequency * wavelength = f * lambda
343
Period equation (T)
= 1 / frequency = 1 / f
344
Angular frequency (omega)
= 2 pi frequency = (2 pi) / period
| = 2 pi f = (2 pi) / T
345
Speed of sound equation (v)
= square root (B / rho)
346
Doppler effect (f')
= f [(v +/- vd) / (v -/+ vs)]
347
Intensity (I)
= P / A = Power / Area
348
Sound level (beta)
= 10 log (I / Io)
349
Change in sound level (beta f)
= beta i + 10 log (If / Ii)
350
Frequency of a standing wave in strings and open pipes (f)
= n v / 2 L
351
Frequency of a standing wave in closed pipes (f)
= n v / 4 L
352
Transverse waves
Have oscillations of wave particles perpendicular to the direction of wave propagation
353
Longitudinal waves
Have oscillations of wave particles parallel to the direction of wave propagation
354
Displacement in a wave
Refers to how far a point is from the equilibrium position, expressed as a vector quantity
355
Amplitude in a wave
The magnitude of its maximal displacement
356
Crest
The maximum point of a wave (point of most positive displacement)
357
Trough
The minimum point of wave (point of most negative displacement)
358
Wavelength in a wave
The distance between two crests or two troughs
359
Constructive interference
Occurs when waves are exactly in phase with each other
| The amplitude of the resultant wave is equal to the sum of the amplitudes of the two interfering waves
360
Destructive interference
Occurs when waves are exactly out of phase with each other
| The amplitude of the resultant wave is equal to the difference in amplitude between the two interfering waves
361
Partially constructive and partially destructive interference
Occur when two waves are not quite perfectly in or out of phase with each other
The displacement of the resultant wave is equal to the sum of the displacements of the two interfering waves
362
How are standing waves produced?
By constructive and destructive interference of two waves of the same frequency traveling in opposite directions in the same space
363
Antinodes
Points of maximum oscillation
364
Nodes
Points where there is no oscillation
365
Resonance
The increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object
366
Damping (attenuation)
A decrease in amplitude (and therefore intensity) over distance and energy is lost due to applied or nonconservative forces
367
Where does sound propagate the fastest?
In solids
368
Where does sound propagate the slowest?
In gases
369
What happens to the speed of sound as the medium's density increases?
Decreases
370
Doppler effect
A shift in perceived frequency of a sound compared to the actual frequency of the emitted sound when the source of the sound and its detector are moving relative to one another
371
How do shock waves (sonic booms) form?
When the source is moving at or above the speed of sound
372
In what kind of pipe is the length of the pipe equal to some multiple of half-wavelengths?
Strings (pipes closed at both ends) and open pipes (pipes open at both ends)
373
In what kind of pipe is the length of the pipe equal to some odd multiple of quarter-wavelengths?
Closed pipes (pipes closed at only one end)
374
How do ultrasound machines calculate distance?
Based on the travel time of the reflected sound
375
When do shock waves have the greatest impact?
When the source is traveling at exactly the speed of sound
376
Surface area of a sphere
= 4 pi r^2
377
Log 100
= 2
378
Order the types of electromagnetic radiation from highest energy to lowest energy
Gamma-rays > x-rays > ultraviolet > visible light > infrared > microwaves > radio
379
What properties of light follow the same trend as energy?
Frequency : as energy increases so does frequency
380
Are light waves longitudinal or transverse waves?
Transverse
381
Why are light waves transverse?
Because the direction of propagation is perpendicular to the direction of oscillation
382
What are the boundaries of the visible spectrum?
400 nm - 700 nm
383
How does the range of the visible spectrum compare to the range of the full electromagnetic spectrum?
It is very small since the entire electromagnetic spectrum ranges from 0 to 10^9 m
384
What properties of light follow the opposite tend as energy?
Wavelength : as energy increases, wavelength decreases
385
o is positive in a mirror
Object is in front of the mirror
386
i is positive in a mirror
Image is in front of the mirror (real image)
387
r is positive in a mirror
Mirror is concave (converging)
388
f is positive in a mirror
Mirror is concave (converging)
389
m is positive in a mirror
Image is upright (erect)
390
o is negative in a mirror
Object is behind the mirror
391
i is negative in a mirror
Image is behind the mirror (virtual image)
392
r is negative in a mirror
Mirror is convex (diverging)
393
f is negative in a mirror
Mirror is convex (diverging)
394
m is negative in a mirror
Image is inverted
395
o is positive in a lens
Object is on the same side of lens as light source
396
i is positive in a lens
Image is on opposite side of lens from light source (real image)
397
r is positive in a lens
Lens is convex (converging)
398
f is positive in a lens
Lens is convex (converging)
399
m is positive in a lens
Image is upright (erect)
400
o is negative in a lens
Object is on opposite side of lens from light source
401
i is negative in a lens
Image is on same side of lens as light source
402
r is negative in a lens
Lens is concave (diverging)
403
f is negative in a lens
Lens is concave (diverging)
404
m is negative in a lens
Image is inverted
405
Real image in mirrors
Image that is in front of the mirror
406
Concave mirror
Converging mirror
407
Virtual image in mirrors
Image that is behind the mirror
408
Convex mirror
Diverging mirror
409
Real image in lenses
Image is on the opposite side of the lens from the light source
410
Convex lens
Converging lens
411
Virtual image in lenses
Image is on the same side of the lens as the light source
412
Concave lens
Diverging
413
Is the incident angle always measured with respect to the normal?
Yes
414
Describe the bending of light when moving from a medium with low refractive index to one with high refractive index
The light will bend towards the normal
415
Describe the bending of light when moving from a medium with high refractive index to one with low refractive index
The light will bend away from the normal
416
Dispersion
The tendency for different wavelengths of light to experience different degrees of refraction in a medium, leading to separation of light into the visible spectrum (a rainbow)
Involves the breaking up go polychromatic light into its component wavelengths, because the degree of refraction depends on the wavelength
417
Aberration
Whether spherical or chromatic, is the alteration or distortion of an image as a result of an imperfection in the optical system
418
What are the two mathematical relationships between image distance and object distance?
1 / f = 1 / o + 1 / i
| m = - i / o
419
What happens if the incident angle is larger than the critical angle?
Total internal reflection will occur
420
How does the diffraction patter for a single slit differ from a slit with a thin lens?
Diffraction through a single slit does not create characteristic fringes when projected on a screen, although the light does spread out. When a lens is introduced into the system, the additional refraction of light causes constructive and destructive interference, creating fringes.
421
What wave phenomenon do diffraction fringes result from?
Constructive and destructive interference between light rays
422
How does double-slit diffraction and interference differ from single-slit diffraction?
The image formed during double0slit diffraction contains fringes because light rays constructively and destructively interfere. A single slit forms an image of a wide band of light, spread out from its original beam.
423
Are the maxima in diffraction patterns always equidistant between two minima?
Yes
Maxima and minima alternate in a diffraction pattern. A maximum is equidistant between two minima, and a minimum is equidistant between two maxima.
424
Plane-polarized light
Contains light waves with parallel electric field vectors
425
Circularly polarized light
Selects for a given amplitude and has a continuously rotating electric field direction
All the light rays have electric fields with equal intensity
426
How does the application of a policed filter impact the wavelength of light passing through the filter?
Plane polarization has no effect on the wavelength, or frequency, or speed of light. Polarization does affect the amount of light passing through medium and light intensity
427
Speed of light from frequency and wavelength (c)
= f * lambda
428
Law of reflection
Theta 1 = theta 2
429
Optics equation
1 / f = 1 / o + 1 / i = 2 / r
430
Magnification (m)
= - i / o
431
Index of refraction (n)
= c / v
432
Snell's law
n1 sin (theta 1) = n2 sin (theta 2)
433
Critical angle (theta c)
= sin^-1 (n2 / n1)
434
Lensmaker's equation
1 / f = (n - 1) (1 / r1 - 1 / r2)
435
Power (P)
= 1 / f
436
Focal length of multiple lens system
1 / f = 1 / f1 + 1 / f2 + ...
437
Power of multiple lens system
P = P1 + P2 + ...
438
Magnification of multiple lens system
m = m1 * m2 * ...
439
Positions of dark fringes in slit-lens setup
alpha sin (theta) = n * lambda
440
Positions of dark fringes in double-slit setup
d sin (theta) = (n + 0.5) * lambda
441
Are electromagnetic waves transverse or longitudinal waves?
Transverse
442
Electromagnetic waves
Transverse waves that consist of an oscillating electric field and an oscillating magnetic field, perpendicular to one another and to the direction of wave propagation
443
Electromagnetic spectrum
The range of frequencies and wavelengths found in electromagnetic waves
444
Violet wavelength
400 nm
445
Red wavelength
700 nm
446
Reflection
The rebounding of incident light waves at the boundary of a medium
447
Law of reflection
The incident angle will equal the angle of reflection, as measured from the normal
448
Spherical mirrors
Have centers and radii of curvature as well as focal points
449
What kind of images do concave (converging) mirrors produce?
Real and inverted OR virtual and upright, depending on the placement of the object relative to the focal point
450
What kind of images do convex (diverging) mirrors produce?
Virtual and upright images
451
What kind of images do plane mirrors produce?
Virtual and upright images behind the mirror (these images are the same size as the objects)
452
Plane mirrors
Have infinite radii or curvature
453
Refraction
The bending of light as it passes from one medium to another
454
What changes the speed of light?
Index of refraction
455
What causes refraction?
The change in the speed of light as it passes from one medium into another
456
What does the amount of refraction depend on?
Wavelength
457
What causes dispersion of light through a prism?
The fact that the amount of refraction depends on the wavelength of the light involved
458
Snell's law (the law of refraction)
There is an inverse relationship between the index of refraction and sine of the angle of refraction (measured from the normal)
459
Total internal reflection
Occurs when light cannot be refracted out of a medium and is instead reflected back inside the medium. This happens when light moves from a medium with a higher index of refraction to a medium with a lower index of refraction with a high incident angle
460
Critical angle
The minimum incident angle at which total internal reflection occurs
461
Where is the focal point in a thin symmetrical lens?
On both sides of the lens
462
What kind of images do convex (converging) lenses produce?
Real and inverted OR virtual and upright
463
What kind of images do concave (diverging) lenses produce?
Virtual and upright images
464
When is it important to use the lenasmaker's equation?
When working with lenses of non-negligible thickness
465
Diffraction
The bending and spreading out of light waves as they pass through a narrow slit
It may produce a large central light fringe surrounded by alternating light and dark fringes with the addition of a lens
466
Does interference support the wave theory of light?
Yes
467
Young's double-slit experiment
Shows the constructive and destructive interference of waves that occur as light passes through parallel slits, resulting in minima (dark fringes) and maxima (bright fringes) of intensity
468
How is plane-polarized light created?
By passing unpolarized light through a polarizer
469
How is circularly polarized light created?
By exposing unpolarized light to special pigments or filters
470
Where to plane mirrors project the images?
As far away as the object is
471
In concave mirror, if the object is placed at the center of the mirror's curvature, what is the object distance?
2f
472
What changes as light rays travel from one medium to another?
The wavelength and speed
473
What remains constant as light rays travel from one medium to another?
The frequency and period
474
A source of light passes through three plane polarizers. The first two polarizers are in the same direction, while the third is rotated 90 degrees with respect to the second polarizer. What happens to the light at the third polarizer?
It will not pass through the third polarizer because all the light rays will be oriented in the direction dictated by the first and second polarizers.
475
What does the degree of refraction depend on?
Wavelength
476
Polarization
The alignment of the electric field component of light waves
477
Where is a real image projected in a convex lens system?
Farther than the focal point
478
Where is a virtual image projected in a convex lens system?
Closer than the focal point (i.e. between the lens and the focal point)
479
For a single mirror or lens system, is the real image inverted or erect?
Inverted
480
For a single mirror or lens system, is the virtual image inverted or erect?
Erect
481
Sin (45 degrees)
= 0.707 = square root of 2 / 2
482
What happens to the light passing through a narrow opening if the opening narrows?
The light waves spread even more
483
What happens to the light passing through a narrow opening and a lens if the opening narrows?
The central maximum (the brightest and most central fringe) becomes wider
484
What happens to the light passing through a narrow opening if a lens is introduced?
A pattern consisting of alternating bright and dark fringes can be observed
485
How does the work function relate to the energy necessary to emit an electron from a metal?
The work function describes the minimum amount of energy necessary to emit an electron. Any additional energy from a photon will be converted to excess kinetic energy during the photoelectric effect
486
What does the threshold frequency depend upon?
The chemical composition of a material (that is, the identity of the metal)
487
What electrical phenomenon results from the application of the photoelectric effect?
The accumulation of moving electrons creates a current during the photoelectric effect
488
What determines the absorption spectrum of a single atom?
The energy differences between ground-state electrons and higher-level electron orbits determine the frequencies of light a particular material absorbs (its absorption spectrum)
489
Can small changes in chemical structure (e.g. protonation, deprotonation, change in oxidation state, change in bond order) impact light absorption and emission patterns?
Yes
490
During which electronic transitions is photon emission most common?
When electrons transition from a higher-energy state to a lower-energy state
491
What causes fluorescence?
Energy transition
492
Fluorescence
A special stepwise photon emission in which an excited electron returns to the ground state through one or more intermediate excited states
Each step has less energy than the absorbed light and is within the visible range of the electromagnetic spectrum
493
When can materials release photons of light in the visible range?
When the energy transition is smaller than the initial energy absorbed
494
Strong nuclear force
One of the four primary forces
| Provides the adhesive force between the nucleons (protons and neutrons) within the nucleus
495
Mass defect
The apparent loss of mass when nucleons come together, as some of the mass is converted into energy during nuclear fusion
The difference between the mass of the unbounded nucleons and the mass of the bonded nucleons within the nucleus
496
Binding energy
Energy holding nucleons together
497
What are the four fundamental forces of nature?
Gravitational force, electrostatic force, stone nuclear forces and weak nuclear forces
498
How does the mass defect relate to the binding energy?
There is a transformation of nuclear matter to energy with a resultant loss of matter
E = m c^2
499
Do both nuclear fission and nuclear fusion release energy?
Yes
500
What is the size of reactant particles in nuclear fission?
Large (actinides and lanthanides)
501
What is the size of reactant particles in nuclear fusion?
Small (H and He)
502
What is the change in nuclear mass during a reaction with nuclear fission?
Decrease
503
What is the change in nuclear mass during a reaction with nuclear fusion?
Increase
504
What kind of particle does alpha decay emit?
He (2, 4)
505
What kind of particle does beta-negative decay emit?
1 electron (in the products) and antineutrino
506
What kind of particle does beta-positive decay emit?
1 positron (in the products) and neutrino
507
What kind of particle does gamma decay emit?
Neutron, gamma ray
508
What kind of particle does electron capture emit?
1 electron absorbed from the inner shell (in the reactants)
509
delta Z of alpha decay
-2
510
delta Z of beta-negative decay
+1
511
delta Z of beta-positive decay
-1
512
delta Z of gamma decay
0
513
delta Z of electron capture
-1
514
delta A of alpha decay
-4
515
delta A of beta-netative decay
0
516
delta A of beta-positive decay
0
517
delta A of gamma decay
0
518
delta A of electron capture
0
519
How many half-lives are necessary for the complete decay of a radioactive sample?
Because the amount remaining is cut in half after each half-life, the portion remaining will never quite reach zero. This is mostly a theoretical consideration; "all" of a sample is considered to have decayed after 7 to 8 half-lives.
520
Which type of nuclear decay could be detected in an atomic absorption spectrum?
Because gamma radiation produces electromagnetic radiation (rather than nuclear fragments), it can be detected on an atomic absorption spectrum
521
Energy of a photon of light (E)
= h f
522
Maximum kinetic energy of an electron in the photoelectric effect (K max)
= h f - W
523
Work function (W)
= h fT
524
Mas defect and energy (E)
= m c^2
525
Nuclear decay (general form)
A. A'
X --->. Y + emitted decay particle
Z. Z'
526
Alpha decay
A. A - 4. 4
X --->. Y + alpha
Z. Z - 2. 2
527
Beta-negative decay
A. A
X --->. Y + beta-
Z. Z + 1
528
Beta-positive decay (positron emission)
A. A
X --->. Y + beta+
Z. Z - 1
529
Gamma decay
A. A
X* --->. X + gamma
Z. Z
530
Electron capture
A. A
X + e- --->. Y
Z. Z - 1
531
Rate of nuclear decay
delta n / delta t = - lambda n
532
Exponential decay (n)
= no e^(- lambda t)
533
Decay constant (lambda)
= ln 2 / T1/2 = 0.693 / T1/2
534
ln 2
= 0.693
535
Photoelectric effect
The ejection of an electron from the surface of a metal in response to light
Occurs when a photon of sufficiently high energy stakes an atom with a sufficiently low work function
536
Threshold frequency
The minimum light frequency necessary to eject an electron from a given metal
537
Work function
The minimum energy necessary to eject an electron from a given metal
538
What does the value of the work function depend on>
The metal used
539
Planck's constant (h)
= 6.626e-34 m^2 kg / s
540
What happens to the kinetic energy the ejected electron can posses if the energy of the incident photon above the work function increases?
Increases
541
Current
Created by the ejected electrons
542
What is the magnitude of current proportional to?
The intensity of the incident beam of light
543
Bohr model of the atom
Electron energy levels are stable and discrete, corresponding to specific orbits
An electron can jump from a lower-energy to a higher-energy orbit by absorbing a photon of light of the same frequency as the energy difference between the orbitals
When an electron falls from a higher-energy to a lower-energy orbit, it emits a photon of light of the same frequency as the energy difference between the orbits
544
How may the absorption spectra be impacted?
By small changes in molecular structure
545
Nuclear binding energy
The amount of energy that is released when nucleons bind together
546
Nucleons
Protons and electrons
547
How is the atom's nucleus stabilized?
With more binding energy per nucleon release
548
Do unbounded constituents have more or less energy than bonded constituents?
More
549
Do unbounded constituents have more or less energy than bonded constituents?
More
550
Fusion
Occurs when small nuclei combine into larger nuclei
551
Fission
Occurs when a large nucleus splits into smaller nuclei
552
Radioactive decay
The loss of small particles from the nucleus
553
Alpha decay
The emission of an alpha particle, which is a helium nucleus
554
Beta-negative decay
The decay of a neutron into a proton, with emission of an electron and an antineutrino
555
Beta-positive decay (positron emission)
The decay of a proton into a neutron, with emission of a positron and a neutrino
556
Gamma decay
The emission of a gamma ray, which converts a high energy nucleus into a more stable nucleus
557
Electron capture
The absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron
558
Half-life
The amount of time required for half of a sample of radioactive nuclei to decay
559
Exponential decay
The rate at which radioactive nuclei decay is proportional to the number of nuclei that remain
560
Does ultraviolet light have higher or lower frequency than visible light?
Higher
561
Does ultraviolet light have higher or lower wavelength than visible light?
Lower
562
Does ultraviolet light have higher or lower energy than visible light?
Higher
563
How is the number of incident photons affected with respect to intensity?
It increases as the intensity increases (provided that the frequency of the light remains above the threshold)
564
How is the number of electrons ejected affected with respect to the number of incident photons?
It increases as the number of incident photons increases (provided that the frequency of the light remains above the threshold)
565
How is current affected with respect to the number of electrons ejected?
It increases as the number of electrons ejected increases (provided that the frequency of the light remains above the threshold)
566
The frequency of light will determine the kinetic energy of the ejected electrons under what conditions?
Only when the frequency of light is above the threshold frequency
567
The intensity of the light will determine the number of electrons ejected per time (the current) under what conditions?
Only when the frequency of light is above the threshold frequency
568
Mass defect calculation
= the mass of each of the protons and neutrons in the unbound state added together minus the mass of the formed (bound) nucleus
569
Binding energy (E)
= m c^2
570
A graph of an exponential decay process is created. The y-axis is the natural logarithm of the ratio of the number of intact nuclei at a given time to the number of intact nuclei at time t=0. The x-axis is time. What does the slope of such a graph represent?
- lambda
The expression:
n = no e^(-lambda t)
is equivalent to:
n / no = e^(-lambda t)
Taking the natural logarithm of both sides, we get:
ln (n / no) = -lambda t
From this expression, plotting ln (n / no) v. t will give a straight line with a slope of - lambda
571
When rounding two numbers containing decimals, in which direction should each number go for multiplication?
Adjust the two decimals in opposite directions : if one number is rounded up, the other number should be rounded down
572
When rounding two numbers containing decimals, in which direction should each number go for division?
Adjust the two decimals in the same direction : if one number is rounded up, the other number should also be rounded up
573
Simplify: (a + b)^2
a^2 + 2ab + b^2
574
Simplify: (a^2 + 2a^2) / 5a^3
3a^2 / 5a^3 = 3 / 5a
575
Simplify: log a (a)
1
576
Simplify: log (a^3) - log (a)
log (a^3 / a) = log (a^2) = 2 log a
577
Estimate: square root (392)
```
Answer is between:
square root (361) and square root (400)
```
Answer is between 19 and 20
= square root (4) * square root (49) * square root (2)
= 2 * 7 * 1.4
= 14 * 1.4
= 19.6 (actual 19.8)
578
Estimate: log (7,426,135,420)
= log (7.4e9)
= 9 + 0.74
= 9.74 (actual 9.87)
579
During vector addition, how is the angle of the resultant calculated?
The value of a trigonometric function calculated from the dimensions of the resultant vector is used in the inverse tangent function to calculate the resultant vector angle
580
How is sine calculated given the dimensions of a right triangle?
Opposite / Hypotenuse
581
How is cosine calculated given the dimensions of a right triangle?
Adjacent / Hypotenuse
582
How is tangent calculated given the dimensions of a right triangle?
Opposite / Adjacent
583
Is it only the angles in right triangles that have characteristic values of the trigonometric functions?
No
While calculating the values or sine, cosine and tangent is more complicated in a triangle that does not contain a right angle, all possible angles do still have characteristic trigonometric values
584
How can angles be calculated?
With inverse trigonometric ratios
585
What does it mean for two variables to have a direct relationship?
As one variable increases, so does the other
| As one variable decreases, so does the other
586
What does it mean for two variables to have an inverse relationship?
As one variable increases, the other decreases
| As one variable decreases, the other increases
587
Substitution
1. Solve one equation for one variable in terms of the other
| 2. Substitute this expression into the other equation
588
Setting equations equal
(A modified version of substitution)
| Solve both equations for the same variable and set them equal to each other
589
Elimination
1. Multiply or divide one (or both) equations so that the coefficient in front of one of the variables is the same in both equations
2. Add or subtract the equations to eliminate one of the variables
590
x^0
= 1
591
x^a * x^b
= x^(a+b)
592
x^a / x^b
= x^(a-b)
593
(x^a)^b
= x^(ab)
594
(x/y)^a
= x^a / y^a
595
x^-a
= 1 / x^a
596
x^(a/b)
= b square root (x^a)
597
square root 2
= 1.4
598
square root 3
= 1.7
599
log a (1)
= 0
600
log a (a)
= 1
601
log (a x b)
= log a + log b
602
log (a / b)
= log a - log b
603
log (a^b)
= b log (a)
604
log (1 / a)
= - log (a)
605
log (x)
= ln (x) / 2.303
606
log (n x 10^m)
= m + 0.n
607
sin (theta)
= opposite / hypotenuse = a / c
| = cos (90 - theta)
608
cos (theta)
= adjacent / hypotenuse = b / c
609
tan (theta)
= opposite / adjacent = a / b
610
Fahrenheit (F)
= 9/5 C + 32
611
Kelvin (K)
= C + 273
612
In measurements, is the last digit considered a significant figure?
No
613
Significant figures in addition
The answer must have the same number of decimal places as the number with the fewest number of decimal places
614
Significant figures in subtraction
The answer must have the same number of decimal places as the number with the fewest number of decimal places
615
Significant figures in multiplication
The answer must have the same number of significant figures as the number with the fewest number of significant figures
616
Significant figures in division
The answer must have the same number of significant figures as the number with the fewest number of significant figures
617
What is the inverse of exponents?
Logarithms
618
What is the base of natural logarithms?
e
619
What is the base of common logarithms?
10
620
2^3 = 8 in log form
log base 2 of 8 = 3
621
pH equation
= pKa + log ([A-] / [HA])
622
log (1)
= 0
623
How can the value of a natural logarithm be converted to the value of a common logarithm?
The normal logarithm is divided by a constant
624
|sin (theta) x cos (theta)|
|sin (theta)| + |cos (theta)|
625
sin (theta) / cos (theta)
= tan (theta)
626
tan (90)
= undefined
627
What forces are acting on an object in uniform circular motion?
Centripetal force
628
Errors or biases during publication of results are most likely to affect which stages of the scientific method?
Errors during publication of current studies adversely affect the quality of future experimentation by providing an incomplete or flawed research base. Without accurate resources, subsequent hypotheses are likely to be flawed.
629
An experiment with an improperly tared (zeroed) mass balance would suffer from what type of error?
Inaccuracy error
630
What is the purpose of a control during experiments?
Controls in experiments help to establish causality by demonstrating that the outcome does not occur in the absence of an intervention
631
What characteristics of experimental research would be reduced in the absence of a control?
Controls are used to keep the manipulations of different systems as similar as possible, or as a known standard against which to judge an experimental manipulation. WiWithout controls, it is far more difficult to establish causality.
632
Can a researcher who fails to demonstrate temporality still provide evidence for a causal relationship by satisfying the rest of Hill's criteria?
No
Temporality is the only necessary criterion from Hill's criteria. If temporality is not satisfied, the relationship cannot be said to be causal. The addition of other criteria increases the probability of a causal relationship, assuming that temporality has not been invalidated.
633
Observational research
Does not involve manipulation of the subject's environment
634
Experimental research
Involves manipulation of the subject's environment
635
Bias
A systematic (unidirectional) error that occurs during the selection of subjects or the measurement and collection of data
636
Confounding
An error that occurs during data analysis, in which an association is erroneously drawn between two variables because of a shared connection to a third variable
637
Which is more conclusive: observational or experimental research?
Experimental research
638
Which is more subjective: observational or experimental research?Less conclusive and more subjective than experimental research
Observational research
639
Autonomy in medical ethics
The right of an individual to make decisions on his or her own behalf and to have those decisions be respected
640
Respect for persons in research ethics
Requires honesty, confidentiality, informed consent, and freedom from coercion
641
During study design, a company wishing to market a drug to severe diabetics proposes to enroll only mild diabetics. Which principle of research ethics is the company violating? Are there any research concerns in this proposed study besides ethics?
The company is violating the principle of justice by choosing participants that are not part of the target population. The company is also introducing selection bias.
642
Coercive influence
The subject loses autonomy to make the decision to participate
643
Monetary compensation
Does not impact the decision to participate
644
What are some populations that must receive special consideration for coercion?
Children, pregnant women and prisoners
645
Internal validity
The tendency of the same experiment to produce the same results when repeated, and provides support for causality
The identification of causality in a study between the independent and dependent variables
646
External validity (i.e. generalizability)
The ability to take the information generated during research and apply it to a larger group
647
Why might small samples provide insufficient information about a population?
Small samples are subject to more random variation than large samples and is more susceptible to being affected by outliers
648
What qualities must a study have to provide justification for an intervention?
A study must have not statistical significant and clinical significance to provide justification for an intervention. A study without statistical significance may be the result of random chance, whereas one without clinical significance will not impact patients
649
Scientific method
A series of eight steps for the generation of new knowledge
1. Generate a testable question
2. Gather data and resources
3. Form a hypothesis
4. Collect new data
5. Analyze the data
6. Interpret the data and existing hypothesis
7. Publish and verify results
650
FINER method
Assess the value of a research question on the basis of whether or not it is:
```
Feasible
Interesting
Novel
Ethical
Relevant
```
651
Controls
Used to correct for any influences of an intervention that are not part of the model
652
Types of controls
Positive or negative controls
653
Positive controls
Ensure that a change in the dependent variable occurs when expected
654
Negative controls
Ensure that no change in the dependent variable occurs when none is expected
655
Types of errors in measurement
Accuracy (validity) and precision (reliability)
656
Accuracy (validity)
The quality of approximating the true value
657
Precision (reliability)
The quality of being consistent in approximations
658
What kind of research is one consisting of human subjects?
Observational
659
Cohort studies
Record exposures throughout time and then assess the rate of a certain outcome
660
Cross-sectional studies
Assess both exposure and outcome at the same point in time
661
Case-control studies
Assess outcome status and then assess for exposure history
662
What is causality in observational studies supported by?
Hill's criteria
663
Hill's criteria
1. Temporality
2. Strength
3. Dose-response relationships
4. Consistency
5. Plausibility
6. Consideration of alternative explanations
7. Experiments
8. Specificity
9. Coherence
664
Forms of error
Bias, confounding or random error
665
Bias
Systematic and results from a problem during data collection
666
Selection bias
The sample differs from the population
667
What is the most common bias in human subjects research?
Selection bias
668
Detection bias
Arises from education professionals using their knowledge in an inconsistent way by searching for an outcome disproportionately in certain populations
669
Hawthorn effect
Results from changes in behavior - by the subject, experimenter or both - that occur as a result of the knowledge that the subject is being observed
670
Confounding
An error in data analysis that results from a common connection of both the dependent and independent caiciables to a third variable
671
Medical ethics
Refers to the four principles of:
Beneficence
Nonmaleficence
Respect for patient autonomy
Justice
672
How were research ethics established?
By the Belmont Report
673
Research ethics
Respect for persons
Justice
Beneficence
674
Respect for persons in research ethics
Autonomy, informed consent and confidentiality
675
Justice in research ethics
Which study questions are with pursuing and which subjects to use
676
Beneficence in research ethics
Do the most food with the least harm
| Do not perform an intervention without equipoise
677
Equipoise
A lack of knowledge about which arm of the research study is better for the subject
678
Populations
All of the individuals who share a set of characteristics
679
Parameters
Population data
680
Samples
A subset of a population that are used to estimate population data
681
Statistics
Sample data
682
How is an intervention supported?
By statistical and clinical significance
683
Statistical significance
The low likelihood of the experimental findings being due to chance
684
Clinical significance
The usefulness or importance of experimental findings to patient care or patient outcomes
685
What would establish a class causal link: an observational study or an experiment?
Experiment
686
What happens when data is off in a systematic way (reads at a value that is not a true value)?
Bias (lack of validity or accuracy)
687
Does unreliable data suffer from random or systemic error?
Random
688
Does confounding arise from errors in data analysis or data collection?
Data analysis
689
Does invalid data lead to bias or confounding?
Bias
690
What types of data sets are best analyzed using the mean as a measure of central tendency?
A data set with relatively normal distributing (not one that has outliers)
691
Is the mean of a sample considered a parameter?
No; the mean of a sample is a statistic; the mean of a population is a parameter
692
How do the mean, median and mode compare for a right-skewed distribution?
The mean of a right (positively) skewed distribution is to the right of the median, which is to the right of the mode
693
Can data that do not follow a normal distribution be analyzed with measures of central tendency and measures of distribution?
Any distribution can be mathematically or procedurally transformed to follow a normal distribution by virtue of the central limit theory. Regardless, a distribution that is not normal may still be analyzed with these measures.
694
What is the difference between normal or skewed distributions, and bimodal distributions?
Bimodal distributions have two peaks whereas normal or skewed distributions have only one.
695
How to determine outliers from the interquartile range?
Outliers are data points more than 1.5 x IQR below Q1 or above Q3
696
How to determine outliers from the standard deviation?
Outliers are data points more than 3 standard deviations above or below the mean
697
How do range and standard deviation generally relate to one another mathematically?
Where the data is not available, the range can be approximated as four times the standard deviation
698
Why would the average difference from the mean be an inappropriate measure of distribution?
The average distance from the mean will always be zero. This is why, in calculations of standard deviation, we always square the distance from the mean and then take the square root at the end - it forces all of the values to be positive numbers, which will not cancel out to zero.
699
Assume the likelihood of having a male child is equal to the likelihood of having a female child. In a series of ten live births, the probability of having at least one boy is equal to:
The probability of having all girls is (0.5)^10
The probability of having at least one boy is:
1 - (0.5)^10 => 99.90%
700
Independence
A condition of events wherein the outcome of one event has no effect on the outcome of the other
701
Mutual exclusivity
A condition wherein two outcomes cannot occur simultaneously
702
Exhaustiveness
There are no other possible outcomes
703
Hypothesis tests
Used to validated or invalidate a claim that two populations are different, or that one population differs from a given parameter
We calculate a p-value and compare it to a chosen significance level (alpha) to conclude if an observed difference between two populations (or between a population and the parameter) is significant or not
Use a known distribution to determine whether a hypothesis of no difference (the null hypothesis) can be rejected
704
Confidence intervals
Used to determine a potential range of values for the true mean of a population
A range of values about a sample mean that are used to estimate the population mean (A wider interval is associated with a higher confidence level, 95% is common)
705
If the p-value is greater than alpha in a given statistical test, what is the outcome of the test?
We fail to reject the null hypothesis
706
How is the p-value calculated during a hypothesis test?
After the test statistic is calculated, a computer program or table is consulted to determine the p-value of the statistic
707
Is power the probability of correctly rejecting the null hypothesis when the alternative hypothesis is true for the population?
Yes
708
What type of data relationship is least likely to require transformation into a semilog or log-log plot?
Linear relationships
709
Pros of a pie chart
Easily constructed
| Useful for categorical data with a small number of categories
710
Pros of a bar graph
Multiple organization strategies
| Good for large categorical data sets
711
Pros of a box plot
Information-dense
| Can be useful for comparison
712
Pros of a map
Provide relevant and integrated geographic and demographic information
713
Pros of a graph
Provide information about relationships
| Useful for estimation
714
Pros of a table
Categorical data can be presented without comparison
| Does not require estimation for calculations
715
Cons of a pie chart
Easily overwhelmed with multiple categories
| Difficult to estimate values with circles
716
Cons of a bar graph
Axes are often misleading because of sizable breaks
717
Cons of a box plot
May not highlight outliers or mean value of a data set
| Only useful for numerical data
718
Cons of a map
May only be used to represent at most two variables coherently
719
Cons of a graph
Axis labels and logarithmic scales require careful interpretation
720
Cons of a table
Disorganized or unrelated data may be presented together
721
Exponential curve
Has a steep component
| Has horizontal symptoms and become flat on one side
722
Parabolic curve
Has a steep component
| Is symmetrical and has steep components on both sides of a center point
723
Is statistical significance a sufficient criteria to enact policy change?
No : There must be practical (clinical) as well as statistical significance for a conclusion to be useful
724
Are two variables that are causally related also correlated with each other?
Yes
725
Median position
= (n + 1) / 2
726
Interquartile range (IQR)
= Q3 - Q1
727
Standard deviation
= square root ([{x1 - mean}^2 + {x2 - mean}^2 + ...] / [n - 1])
728
Probability of two independent events co-occurring
P(A ∩ B) = P(A and B) = P(A) x P(B)
729
Probability of at least one event occurring
P(A U B) = P(A or B) = P(A) + P(B) - P(A and B)
730
Measures of central tendency
Provide a single value representation for the middle of a group of data
731
Arithmetic mean (average)
Measure of central tendency that equally weighs all values
| It is most affected by outliers
732
Median
The value that lies in the middle of the data set
| Fifty percent of data points are above and below the median
733
Mode
The data point that appears most often; there may be multiple (or zero) modes in a data set
734
How are distributions classified?
By measures of central tendency and measures of distribution
735
Normal distribution
Symmetrical
The mean, median and mode are all the same
68% of data points occur within one standard deviation of the mean
95% of data points occur within two standard deviations of the mean
99% of data points occur within three standard deviation s of the mean
736
Standard distribution
A normal distribution with a mean of zero and a standard deviation of one
Used for calculations
68% of data points occur within one standard deviation of the mean
95% of data points occur within two standard deviations of the mean
99% of data points occur within three standard deviation s of the mean
737
Skewed distribution
Has differences in its mean, median and mode
738
What is the direction of a skew?
The direction of the tail of the distribution
739
Bimodal distribution
Has multiple peans, although not necessarily multiple modes
740
Range
The difference between the largest and smallest values in a data set
741
Interquartile range
The difference between the value of the third quartile and first quartile
Used to determine outliers
742
Standard deviation
A measure of variability about the mean
| Used to determine outliers
743
Outliers
May be a result of true population variability, measurement error or a non-normal distribution
744
When are procedures for handling outliers formulated?
Before the beginning of a study
745
Does the probability of an independent event change based on the outcome of another event?
No
746
Does the probability of a dependent event change based on the outcome of another event?
Yes
747
Mutually exclusive outcomes
Outcomes that cannot occur simultaneously
748
Null hypothesis
A hypothesis of no difference
749
How is a finding determined to be statistically significant?
By the comparison of a p-value to the selected significance level (alpha)
750
Common significance level (alpha)
0.05
751
Pie chart (circle chart)
Used to compare categorical data
752
Bar chart
Used to compare categorical data
753
Histogram
Used to compare numerical data
754
Box plot (box-and-whisker plot)
Used to compare numerical data
755
Maps
Used to compare up to two demographic indicators
756
How can linear, semilog and log-log plots be distinguished?
By their axes
757
Which plot is easiest when trying to find the slope?
Linear
758
Tables
May contain related or unrelated categorical data
759
How are correlation and causation linked?
By Hill's criteria
760
In a sample of hospital patients, the mean age is found to be significantly lower than the median. What is the shape of the distribution?
Skewed to the left : The mean is to the left of the median, which implies that the tail of the distribution is on the left side
761
A hypothesis test was correctly conducted and the experimenter failed to reject the null hypothesis. What must be true?
The p-value was greater than alpha and a type I error did not occur :: Type I error occurs when the null hypothesis is incorrectly rejected :: If we failed to reject the null hypothesis, then the p-value must be greater than the significance level
762
A 95% confidence interval will fall within what distance from the mean?
+/- 2 standard deviations
763
Which measure of distribution is most useful for determining probabilities?
Standard deviation because it is the most closely linked to the mean of a distribution and can be used to calculate p-values, which are probabilities (specifically, p-values are the probability that an observed difference between two populations is due to chance)
764
What does low power in a study mean?
If a study has low power, it is more difficult to get results that are statistically significant.
765
What corresponds to the probability of a type I error?
Significance level (alpha)
766
Type I error (alpha)
The probability of mistakenly rejecting the null hypothesis
| We set the type I error level by selecting a significance level (alpha)
767
Power (1 - beta)
Correctly rejecting the null hypothesis
768
Confidence
Correctly failing to reject the null hypothesis
769
Type II error (beta)
Mistakenly not rejecting the null hypothesis
