Physics Flashcards
1
Q
How does an insulator become charged?
A
Electrons are transferred from one material to another by friction
2
Q
What is charging caused by?
A
A loss or gain of electrons
3
Q
What is important to remember about like charges?
A
They will repel
4
Q
What is important to remember about unlike charges?
A
They attract
5
Q
What happens when an appliance short circuits?
A
The live wire of an appliance touches the neutral wire
6
Q
What is an earth wire used for?
A
If there is a fault in the circuit, the earth wire carries the charge into the ground
7
Q
Circuit symbol for a cell
A
A longer vertical line parallel to a shorter parallel line on the right
8
Q
Circuit symbol for a battery
A
Multiple cells joined together
9
Q
Circuit symbol for lamp
A
Circle with a cross inside
10
Q
Circuit symbol for a resistor
A
A clear rectangle
11
Q
Circuit symbol for variable resistor
A
A rectangle with a diagonal arrow pointing from bottom left to top right
12
Q
Circuit symbol for ammeter
A
Circle with an A inside
13
Q
Circuit symbol for voltmeter
A
Circle with a V inside
14
Q
Circuit symbol for switch
A
Two circles connected by a straight line
15
Q
Circuit symbol for diode
A
A circle with a triangle and straight line inside
16
Q
What is the difference between direct and alternating current?
A
An alternating current repeatedly reverses direction
17
Q
What is the difference between conductors and insulators?
A
A conductor allows energy to pass through it whereas an insulator doesn’t
18
Q
Examples of conductors
A
Copper and aluminium
19
Q
Examples of insulators
A
Plastics and rubber
20
Q
Equation for current
A
Charge flow / time
21
Q
What are voltmeters used for?
A
Measures the potential difference across a component
22
Q
Equation for resistance
A
Potential difference / current
23
Q
What does the V-I graph for a fixed resistor look like?
A
A diagonal line from bottom left to top right directly through the origin
24
Q
What does the V-I graph for a filament lamp look like?
A
A curve from bottom left to top right passing directly through the origin
25
Properties of LDRs
Resistance decreases with light intensity
26
Properties of ideal diodes
Allows the current to flow in one direction only
27
What are the rules for current in a series circuit?
The same current passes through each component
28
What are the rules for voltage in a series circuit?
The total potential difference is shared between the components
29
How to calculate the total resistance in a series circuit?
Add the resistances of each component
30
What are the rules for current in a parallel circuit?
The total current is the sum of the currents passing through the branches
31
What are the rule for potential difference in a parallel circuit?
The potential difference across each component is equal
32
Why is the total resistance in a parallel circuit less than that of any individual resistor?
The potential difference remains the same. Adding a resistor increases the current entering the system
Resistance = p.d./i so resistance decreases
33
Equation for voltage
Energy transferred / charge flow
34
What are the two equations for power?
Current x voltage
| Current^2 x resistance
35
What does energy transferred equal?
Power x time
36
What is the north pole of a magnet?
The end of the magnet that will always point north
37
What is the south pole of the magnet?
The end of the magnet that will always point south
38
What is attraction?
The force between two unlike poles
39
What is repulsion?
The force between two like poles
40
Describe the magnetic field around a magnet
Lines point in a direction away from the north pole towards the south, the magnetic field is more concentrated at the poles
41
What is the difference between soft and hard magnets?
Hard magnetic retain their magnetism and are difficult to demagnetize, soft magnetic materials are easy to demagnetize
42
Describe induced magnetism
An unmagnetized material can be magnetized by placing it inside a magnetic field
43
What is the difference between permanent and electromagnetism?
A permanent magnet retains its magnetism over a long period of time, whereas electromagnets can be magnetised and demagnetised
44
How to increase the magnetic field of a solenoid
Increase the strength of the current
| Can reverse its direction by reversing the direction of the current
45
Characteristics of solids
Particles are tightly packed
46
Characteristics of liquids
Particles are packed together but less tightly than solids. Liquids take on the shape of their container
47
Characteristics of gases
Particles are held together loosely
48
What is the effect of temperature on particles?
The particles move faster with more kinetic energy and collide more frequently
49
What is the effect of pressure on particles?
The particles are held closer together so collide more often
50
At constant temperature, what will both pressure and volume be?
Constant
51
What is melting point?
The temperature at which a solid melts
52
What is boiling point?
The temperature at which a liquid turns into a gas
53
What is the latent heat of fusion?
The amount of heat energy required to change 1g of a substance from the solid to liquid state without changing its temperature
54
What is latent heat of vaporisation?
The amount of energy required to change 1g of a substance from the liquid to gaseous state without changing its temperature
55
Equation for density
Mass / volume
56
What happens to density as you move from solid to gas?
It decreases
57
How do you determine density experimentally?
The amount of water displaced when an object is placed in a body of water is its volume. Use this and its mass to calculate density
58
Equation for pressure
Force / area
59
Equation for hydrostatic pressure
h x p x g
h = Height of column
p = density of liquid
g = acceleration of gravity
60
Equation for hydrostatic pressure
h x p x g
h = Height of column
p = density of liquid
g = acceleration of gravity
61
What are thermal conductors?
Materials that allow heat to travel through them
62
What are thermal insulators?
Materials that don't allow heat to travel through them
63
Examples of thermal conductors
Steel, copper, aluminium
64
Examples of thermal insulators
Plastic, wool, foam
65
What factors affect the rate of conduction?
Temperature difference across the material
Thickness of material
Thermal conductivity of material
66
What impact does temperature have on the density of fluid?
Increasing temperature = increased volume = decreased density
67
What will happen to a wire carrying a current in a magnetic field?
It will experience a force
68
How to remember the factors affecting the direction of a force on a wire?
The left hand rule - first finger = field
- thumb = movement
- second finger = current
69
What are the factors affecting the direction of a force on a wire in a magnetic field?
Magnetic field and current
70
What are the factors affecting the magnitude of a force on a wire in a magnetic field?
Size of current, strength of magnet
71
How do you calculate the force on a wire?
Force = magnetic flux density x current x length
72
How is a dc motor constructed?
A coil rotates inside a magnetic field
An electric current is induced
The output comes via split ring output
As the coil turns, the split-ring commutator reconnects The coil the opposite way around each the circuit each half turn
This means that the wire will only be connected to one half of the output
Therefore, the current flows in one direction only
73
What are electromagnets used in
Cranes, motors, doorbells
74
When will a voltage be induced in a wire?
When a wire cuts a magnetic field
75
How does an ac generator work?
The movement of the bar magnet induces a p.d. in the coil
| This p.d. creates a current because the coil is part of a complete circuit
76
When will the outcome of the generator be highest?
When the plane of the coil is parallel to the magnetic field
Use a magnet with a strong magnetic field
More turns on the coil of wire
77
What will the graph of an ac generator look like?
A sin graph
78
What is a step up transformer?
Increase the size of an alternating potential difference
79
What is a step down transformer?
Decreases the size of an alternating potential difference
80
What is the voltage ratio for transformers?
Coils on 1 / coils on 2 = voltage on 1 / voltage of 2
81
What is important about a transformer that is 100% efficient?
It is the total transfer of electrical power - VpIp = VsIs
82
Why is it important that a transformer has a high voltage?
Reduces energy lost in resistance
83
What is a scalar quantity?
Has only magnitude
84
What is a vector quantity?
Has both magnitude and direction
85
What is the difference between speed and velocity?
Speed is a scalar quantity, velocity is a vector
86
What is the difference between distance and displacement?
Distance is a scalar quantity, displacement is a vector
87
Equation for speed
Distance / time
88
Equation for velocity
Change in displacement / time
89
Equation for acceleration
Change in velocity / time
90
What is the gradient of a distance-time graph?
Speed
91
What is the gradient of a displacement-time graph?
Velocity
92
What is the gradient of a speed-time graph?
Acceleration
93
What is the area under a speed-time graph?
Distance travelled
94
What is the gradient of a velocity-time graph?
Acceleration
95
What is the area under a velocity-time graph?
Displacement
96
What does average speed equal?
Total displacement / total time
97
What is the equation of motion?
v^2 - u^2 = 2as
98
What are the different forces?
Weight, normal contact, drag, friction, magnetic, electrostatic, thrust, upthrust, tension and lift
99
What does work equal?
Force x distance
100
What is work done?
Transfer of energy
101
What does gravitational potential energy equal?
Mass x gravitational field strength x height
102
What does kinetic energy equal?
.5 x mass x velocity^2
103
What is the law of the conservation of energy?
Energy can't be created or destroyed, only transformed from one form to another
104
What is wasted energy?
Energy that isn't used in the way that it was intended to
105
Equation for percentage efficiency
(useful output/total output) x 100
106
What does frequency equal?
1 / period
107
What does wave speed equal?
Distance / time or frequency x wavelength
108
Where are neutrons and protons found?
The nucleus
109
Where are electrons found?
Orbitals
110
Charge and mass of neutron
0, 1
111
Charge and mass of proton
1, 1
112
Charge and mass of electron
Very small, 1/2000
113
What is ionisation caused by?
Gain/loss of electrons
114
Where do emissions arise from?
An unstable nucleus
115
What is an atom's half life?
The time taken for half of the unstable nuclei to decay
116
Properties of diodes
No resistance, only allows the current to flow in one direction
117
Properties of thermistors
Resistance decreases with increasing temperature
118
Properties of LDRs
Resistance decreases with increasing light intensity
119
What does the magnetic field pattern around a solenoid look like?
Each field line is a complete loop which bends from one side of the solenoid to the other
120
What is the resultant force?
The effect of multiple forces on an object written as a single force
121
What does the gradient of a force-extension graph equal before the limit of proportionality is reached?
The spring constant
122
What is the elastic limit?
The point at which a spring has been so stretched so much it won't return to its original shape
123
What is Hooke's law?
The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length
124
Equation for Hooke's law
Force = k x Δl
125
Equation for elastic energy
.5 x k x x^2
126
What is Newton's first law?
A body will remain at rest or travel uniformly unless acted on by a resultant external forc
127
What property can change an object's inertia?
Mass
128
What is Newton's second law?
Force = mass x acceleration
129
What is Newton's third law?
Two objects exert equal and opposite forces on eachother
130
Equation for momentum
Mass x velocity
131
Equation for force when using momentum
Force = change in momentum
132
What is the law of the conservation of momentum?
The momentum before a collision = the momentum after
133
What is the value of gravitational field strength?
10 N/kg
134
Equation for weight
Weight = mass x gravitational field strength
135
What is the difference between mass and weight?
Weight is the force exerted by gravity on an object
136
What is terminal velocity?
The velocity reached on an object when the drag force is equal and opposite to the force making it move
137
What factors affect terminal velocity?
The object's mass and surface area
| Gravitational field strength
138
What is free-falling acceleration
An object falling purely under the force of gravity
139
What will happen to an object's temperature when energy is transferred to/from it?
It will increaese/decrease
140
Equation for specific heat capacity
Thermal energy / (mass x Δtemperature)
141
What electromagnetic waves are involved in thermal radiation?
Infrared
142
What material is good at absorbing radiation?
A light coloured/shiny one
143
What factors affect the rate of emission/absorption?
The surface area, volume and material of an object
144
What is the equation for specific latent heat?
Energy / mass
145
Equation for specific heat capacity
m x c x Δt
146
What happens when waves are reflected at a surface?
The reflected ray is at the same angle as the incident ray
147
What happens when waves refract at a boundary?
The waves change both speed and direction
148
What effect does reflection have on frequency, wavelength and direction?
Frequency: same
Wavelength: same
Direction: same
149
What effect does refraction have on frequency, wavelength and direction?
Frequency: same
Wavelength: decreases
Direction: bends towards normal
150
What is the doppler effect?
The change in distance between causer and observer causes a change in frequency and wavelength
151
What does the angle of incidence equal?
The angle of reflection
152
What is nuclide notation?
```
A(X)
Z
Contains Z protons and A-Z neutrons
Atomic mass = A
Charge = +Ze
```
153
How far can alpha radiation penetrate?
It is blocked by paper
154
How far can beta radiation penetrate?
Blocked by aluminium foil
155
How far can gamma radiation penetrate?
Blocked by thick lead sheet
156
Rank the three types of radiation from highest ionising power to weakest
Alpha, beta, gamma
157
Where does background radiation come from?
Radon gas
158
What is an alpha particle made from?
2 protons and 2 neutrons
159
What is a beta particle made from?
An electron
160
What is gamma radiation made from?
Waves
161
What effect does alpha radiation have on atomic number?
Its atomic number decreases by 2
| Its mass number decreases by 4
162
What effect does beta radiation have on atomic number?
The atomic number increases by 1
163
What effect does gamma radiation have on atomic number?
None
164
Which types of radiation can be deflected by electric fields?
Alpha and beta radiation
165
Give two properties of electromagnetic waves
They are transverse waves and travel at the speed of light in a vacuum
166
What are the seven components of the spectrum?
Radio waves, microwaves, IR, visible light, ultraviolet, x-rays, gamma rays
167
Give the wavelengths and frequencies of the component parts of the electromagnetic spectrum
```
Radio waves: 10^3 and 10^4
Microwaves: 10^-2 and 10^8
IR: 10^-5 and 10^12
Visible light: 10^-6
Ultraviolet: 10^-8, 10^15
X-rays: 10^-10 and 10^18
Gamma rays: 10^-12 and 10^20
```
168
What are produced by reflections?
Echoes
169
What is the range of human hearing?
20Hz to 20kHz
170
How is volume related to amplitude?
Volume is proportional to amplitude
171
How is pitch related to frequency?
They are directly proportional
172
How do ultrasounds measure internal boundaries?
When there is a boundary, some ultrasound is reflected back. The time taken is recorded and this is used to work out how far the boundary is
173
How are ultrasounds used for medical imaging?
Wherever there is a boundary, some of the wave is reflected back and detected
The timing and distribution of these echoes are recorded and turned into an image
174
Why is a medium needed for sound?
Sound molecules vibrate and pass the impulse between one another; this can't happen in a vacuum
175
How are sound waves produced?
An object vibrates and transfers this energy to another medium
176
What is the amplitude?
The height of a wave
177
What is the frequency?
The number of oscillations in a given time
178
What is the wavelength?
The difference between crests in successive waves
179
What is the period?
The time taken for one complete wave
180
What is the peak?
The highest point on a wave
181
What is the trough?
The lowest point on a wave
182
What is a compression?
The wave is compressed
183
What is a rarefaction?
The wave is stretched
184
What is important to remember about waves?
They transfer energy without the movement of matter
185
What are transverse waves?
The oscillations are perpendicular to the direction of energy transfer
186
What are longitudinal waves?
The oscillations are parallel to the direction of energy transfer
187
Examples of transverse waves
Electromagnetic waves
188
Examples of longitudinal waves
Sound waves
189
What properties make a good electrical conductor?
Low first ionisation energy, simple material structure
190
How to calculate total resistance in parallel?
1/R1 + 1/R2 + 1/R3 etc
191
What is important to remember about the pressure in a hydraulic system?
It is always constant
192
Volume of a sphere
4/3 x pi x r^3
