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Physics A Level Better One > Electricity > Flashcards

Electricity Flashcards

1
Q

What equation connects V, I and R

A

V = I R

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2
Q

What equation connects R, ρ, L and A

A

R = ρ L / A

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3
Q

What equation connects P, I and V?

A

P = I V

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4
Q

What is P, units?

A

Power, watts

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5
Q

What equation connects P, V and R?

A

P = V^2 / R

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6
Q

What equation connects P, I and R?

A

P = I^2 R

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7
Q

What equation connects Q, I and t?

A

Q = I t

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8
Q

What is Q, units?

A

Charge, coulombs

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9
Q

From which end of the battery does the current flow?

A

Negative to positive

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10
Q

What does the exam board call the flow of electrons from neg to pos?

A

Conventional current

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11
Q

To make the electrons flow they have to flow to a ____ potential?

A

Lower

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12
Q

If you subtract the lower potential from the higher potential, what do you get?

A

Potential difference

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13
Q

The greater the voltage of a battery the _____ the current in a circuit?

A

Bigger

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14
Q

Something that causes difficulty in electrons flowing down a wire is called a _____?

A

Resistance

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15
Q

What is Ohm’s law?

A

The current flowing through a metallic conductor is directly proportional to the potential difference applied across it at a constant temp

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16
Q

V is directly proportional to _?

A

I

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17
Q

What is an Ammeter used to measure?

A

Current

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18
Q

What is an Ammeter always connected in?

A

Series

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19
Q

What is a Voltmeter used to measure?

A

Potential difference

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20
Q

What is a voltmeter always connected in?

A

Parallel

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21
Q

What is the definition of potential difference?

A

The potential difference between two points is the amount of energy transformed when one coulomb of charge is moved between the two points

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22
Q

What is the equation that connects W, Q and V?

A

W = Q V

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23
Q

In a series circuit the current in that particular circuit will be the ____ at every point in the circuit.

A

Same

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24
Q

In a series circuit the p.d across each resistor is ____?

A

Different

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25
Q

In a series circuit the p.d across each resistor is ____?

A

Different

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26
Q

What does the p.d all add up to in a circuit?

A

The battery voltage

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27
Q

In a series circuit V = __________?

A

V1 + V2 + V3`

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28
Q

In a parallel circuit the p.d across each branch in that particular circuit will be ____?

A

Same

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29
Q

In a parallel circuit the current in each branch may be _____?

A

Different

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30
Q

In a parallel circuit all the currents add up to the ________?

A

Supply Current

31
Q

In parallel I =

A

I1 + I2 + I3

32
Q

What is Kirchoff’s first law?

A

At any junction in a circuit the sum of the current flowing into the junction is equal to the sum of the current flowing away from it

33
Q

What is Kirchoff’s second law?

A

In any complete loop of a circuit the sum of the sum of p.d’s equals the source p.d

34
Q

In a series circuit what does Rtotal = ?

A

R1 + R2 + R3

35
Q

In a parallel circuit what does 1/Rtotal = ?

A

1/R1 + 1/R2 + 1/R3

36
Q

What is the equation that connects W, Q and V?

A

W = Q V

37
Q

What is W, unit?

A

Work done, joules

38
Q

What is the equation that connects W, P and t?

A

W = P t

39
Q

When a current flows through a circuit some energy is transformed into ____?

A

Heat

40
Q

When 2+ resistors are connected in series the total p.d is _____ between them

A

Divided

41
Q

In a series circuit the largest resistor has the _______ p.d across it

A

Largest

42
Q

In a series circuit the individual p.ds are the ____ as the power supply

A

Same

43
Q

What does the current/voltage graph look like for a resistor?

A

Straight line through origin to the right, directly proportional

44
Q

What does the current/voltage graph look like for a filament lamp?

A

S shape, to the right, intersecting origin

45
Q

What does the current/voltage graph look like for a diode?

A

Flat then curved up in the upper right quadrant

46
Q

What is the quantity that describes how restive a material is?

A

Resistivity

47
Q

What does EMF stand for?

A

Electromotive force

48
Q

Define EMF

A

The E.M.F of a cell is the voltage across the terminals of a cell when no current is flowing through it

49
Q

What is the internal resistance (r)?

A

The resistance of the cell itself

50
Q

How is internal resistance represented in a circuit diagram?

A

As a circle with r in it around the cell

51
Q

Define electric current

A

The rate of flow of charge in a wire or component

52
Q

What is a superconductor?

A

A wire or device that is made of a material that has 0 resistivity and below a critical temp

53
Q

When would a superconductor lose its superconductivity?

A

If it’s temp is raised above critical temp

54
Q

What are superconductors used to make?

A

High power electromagnets, used in MRI scanners and particle accelerators

55
Q

What components can we see in potential divider circuits?

A

Variable resistors, thermistors, LDRs

56
Q

What can we use potential divider circuits for?

A

Control of light levels, control of temp

57
Q

Define terminal p.d.

A

T.P.D is the voltage that a cell has when current is flowing through it and an external resistor

58
Q

What is the equation connecting ℰ, I, R and r?

A

ℰ = I (R + r)

59
Q

What is ℰ, units?

A

EMF, J/C

60
Q

What is the expanded form of ℰ = I (R + r)?

A

ℰ = IR + Ir

61
Q

What is Ir?

A

P.d across internal resitor

62
Q

What is Ir sometimes referred to as?

A

Lost volts

63
Q

Vout = ?

A

Vin x R2 / R1 + R2

64
Q

What is a regular thermistor called?

A

Negative temperature coefficient

65
Q

What happens as temp decreases for a NTC thermistor?

A

Resistance increases

66
Q

Why would we use a steel core for cables?

A

Increase mechanical strength

67
Q

P.d is proportional to what?

A

R

68
Q

Sum of p.d = ?

A

EMF

69
Q

As light decreases LDR resistance …?

A

Increases

70
Q

More power dissipates in what circuits, why?

A

Parallel, smallest R

71
Q

Is the coulomb an SI unit?

A

No

72
Q

Resolution is what?

A

The smallest dectectable change by a measuring system

73
Q

What is precision?

A

Number of d.p

74
Q

Define potential divider circuit

A

A combination of resistors in series connected across a voltage source (to produce a required pd)

Physics A Level Better One (7 decks)

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