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MCAT PHYSICS > Lect 7: Electricity and Magnetism > Flashcards

Lect 7: Electricity and Magnetism Flashcards

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1
Q

intrinsic property of some subatomic particles
positive and negative 1.6 * 10^-19 C
quantied to discrete levels
SI Unit = Coulomb

A

charge (q)

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2
Q

universe has 0 net charge; Net charge is created by separating electrons from protons
If a negative charge is created, a positive charge must be created

A

law of conservation of charge

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3
Q

describes the magnitude of the force of attraction / repulsion between two charged objects (point charges)

A

Coulomb’s Law

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4
Q

Equation: Coulomb’s Law

A

F = k * q1 * q2 / r^2

Note: k = Coulomb’s constant = 8.9 * 10^9 N*m^2 / C^2

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5
Q

point where the charge of an object is considered to originate

A

center of charge

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6
Q

concept to explain action at a distance

create forces of gravity, electricity, and magnetism

A

field

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7
Q

represent any field
point in the direction of a field: Positive —> Negative
relative distance between lines shows strength of field
can never intersect

A

lines of force

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8
Q

electrostatic force per unit charge
vector in the direction of the field
SI Unit = N/C or V/ m

A

electric field (E)

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9
Q

Equation: Electric Field from a point charge

A

E = k * q / r^2

SI Unit: N / C

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10
Q

Equation: Electrostatic force on a point chargee

A

F = E * q

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11
Q

Equation: Potential Energy (U) of a point charge in an electric field

A

U = F * d = E * q * d
SI Unit: Joule
Note: d = displacement from arbitrary 0 point

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12
Q

the potential for work by an electric field in moving any charge by a distance (d)
SI Unit = Volts (V) and J/C

A

voltage

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13
Q

Equation: Voltage

A

V = E * d

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14
Q

Equation: Voltage due to a point charge

A 
V = k * q / r
SI = V or J/C
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15
Q

Work done by an electric field is _______ of the path because the field conserves mechanical energy

A

independent

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16
Q

movement perpendicular to the electric field doesn’t cause a change in potential; all points on this surface are at the same voltage

A

equipotential surface

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17
Q

created by two opposite charges w/ equal magnitudes; aligns itself in the opposite orientation to the field when placed in an electric field

A

electric dipole

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18
Q

allows electrons to flow relatively freely; holds excess charge on the surface of the material; if uniformly charged, the electric field = 0
Ex: Metal

A

conductor

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19
Q

holds electrons tightly in place; poor conductors

Ex: network solids (glass, diamond)

A

resistors

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20
Q

to charge a conductor w/ a charged object
Ex: negatively charged rod placed near a good conductor that is near a second conductor causes electrons to move from the first to the second conductor, leaving the first one w/ a positive charge

A

induction

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21
Q

a moving charge; scalar quantity
flow is in the direction of POSITIVE charge; created by the flow of electrons but is in the direction that a positive charge would flow
SI = Amp (A) or C/sec

A

current (I)

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22
Q

cyclical pathway for a moving charge

A

circuit

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23
Q

quantitative measure of how a substance resists the flow of charge

A

resistivity (rho)

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24
Q

quantitative measure of an object w/ a certain shape/size to resist flow of charge; if the length of wire / area is cut in half, the object’s ___ is doubled
proportional to LENGTH and inversely proportional to AREA
SI Unit = Ohm (Ω)

A

resistance (R)

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25
Q

product of R and I = voltage (V); equation used to analyze circuits

A

Ohm’s Law

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26
Q

Equation: Ohm’s Law

A

V = I*R

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27
Q

a current flowing into a node must = the current flowing out; (A node is any INTERSECTION of wires)

A

Kirchoff’s 1st rule

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28
Q

voltage around any path in a circuit must sum to 0

A

Kirchoff’s second rule

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29
Q

measurement used to rate batteries, which add energy to increase the voltage between two points
Note: Assume NO internal resistance on MCAT

A

Electromotive Force (EMF)

30
Q

used to temporarily store energy in a circuit in a separated charge

A

capacitor

31
Q

two conductive plates separated by a small distance; 2 plates hold = amounts of opposite charges; creates a constant electric field between the two plates

A

parallel plate capacitor

32
Q

the ability to store charge / unit voltage; a substance with high _____ can store a lot of charge at low voltage
proportional to charge and inversely proportional to voltage
–charge is only on the inside face of each plate; thickness of the plates does not affect charge stored

A

capacitance

33
Q

Each unit of charge added causes the _______ to increase proportionally

A

voltage

34
Q

Equation: Charge w/ capacitance & voltage

graph produces straight line; area under the curve = Energy (Q * V)

A

Q = C * V

35
Q

Equation: Capacitance

SI Unit: Farad (F)

A

C = Q / V

36
Q

Equation: Energy (U) stored by a Capacitor w/ charge and voltage

A

U = 1/2 * Q * V

37
Q

Equation: Energy (U) stored by a Capacitor w/ capacitance and voltage

A

U = 1/2 * C * V^2

38
Q

Equation: Energy (U) stored by a capacitor w/ charge and capacitance

A

U = 1/2 * Q^2 / C

39
Q

substance between the plates of a capacitor; must be an insulator
resists creation of an electric field so plates (capacitor) can store more charge
increases capacitance and amount of Energy (U) stored in the capacitor

A

dielectric

dielectric constant = k

40
Q

components in a row (i.e. train cars)

any two components not separated by a node

A

components in series

41
Q

single components in alternate paths connecting the same nodes

A

components in parallel

42
Q

Equation: Resistors in Series

A

R(eq) = R1 + R2 + R3…….

43
Q

Equation: Resistors in Parallel

A

R(eq) = 1/R1 + 1/R2 + 1/R3……

44
Q

Equation: Capacitors in Series

A

C(eq) = 1/C1 + 1/C2 + 1/C3…

45
Q

Equation: Capacitors in Parallel

A

C(eq) = C1 + C2 + C3…

46
Q

Electric and mechanical are the SAME
used to integrate electricity and mechanics into the same question
Ex: Given V & I of a machine, how quickly can it life a mass (m) to height (h)?

A

Power

47
Q

Set electric power = to mechanical power only when _____

A

energy is dissipated as heat by a resistor

48
Q

Equation: Power w/ current and voltage

A

P = I * V

49
Q

Equation: Power w/ current and resistance

A

P = I^2 * R

50
Q

Equation: Power w/ voltage and resistance

A

P = V^2 / R

51
Q

rate at which heat is generated as current goes through a resistor

A

power dissipated

52
Q

net movement of electrons is unidirectional in a circuit

A

direct current (dc)

53
Q

The movement of _______ creates power

A

electrons

54
Q

current created by oscillating electrons back and forth in simple harmonic motion; voltage or current described by sine wave

A

alternating current (ac)

55
Q

Max current occuren when electrons are at their max ______

A

voltage

56
Q

Equation: Max Voltage

A

V(max) = √2 * V(rms)

57
Q

Equation: V(rms)

A

V(rms) = V(max) / √2

58
Q

Equation: I(rms)

A

I(rms) = I(max) / √2

59
Q

field created by changing electric field; created by moving charge or current; has N and S pole; like poles repel
represented by force lines that point from the north pole to the south pole

A

magnetic field (B)

60
Q

magnetic strength follows inverse square rule except in ______

A

long straight wire

61
Q

Equation: Force on a charge moving through a magnetic field w/ velocity

A

F = q * v * B * sin(ø)

Note: ø = angle between magnetic field and velocity of the charge

62
Q

Force is ______ to Velocity and the Magnetic Field

A

perpendicular

63
Q

Since a force due magnetic field perpendicular to velocity, it does no ______

A

work

64
Q

Magnetic Force changes the ______ but never the _____.

A

direction but never the magnitude

65
Q

a changing magnetic field creates an _____. This process is non-conservative because mechanical energy is transferred into heat energy

A

electric field

66
Q

Equation: circular path of charged particle through a magnetic field

A

q * V * B = m * (v^2 / r)

67
Q

sin(90) = ?

A

= 1

68
Q

cos(90) = ?

A

= 0

69
Q

a moving charge experiences force when moving through a _______

A

magnetic field

70
Q

a magnetic field is generated by ________

A

a moving charge

71
Q

Equation: find circular path of a charged particle through a magnetic field

A

2 * pi (3.14) * r

Note: r = radius of circle

72
Q

Equation: Magnetic Force

A

F = q * v * B

MCAT PHYSICS (5 decks)

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