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NSFC AQA A Level Physics 12C > 5.1 Current electricity > Flashcards

5.1 Current electricity Flashcards

1
Q

Define electric current.

A

Rate of flow of charge

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2
Q

Define potential difference.

A

Work done moving a unit charge between two points.

or work done per unit charge

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3
Q

Define resistance.

A

A measure of how difficult it is for current to flow.

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4
Q

State Ohm’s law.

A

For an Ohmic conductor, current is directly proportional to the potential difference across it.

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5
Q

What does does an IV graph for an Ohmic conductor look like?

A
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6
Q

What does does an IV graph for a semiconducting diode look like?

A
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7
Q

What does does an IV graph for a filament bulb look like?

A
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8
Q

How can you measure current?

A

With an ammeter connected in series.

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9
Q

How can you measure potential difference?

A

With a voltmeter connected in parallel

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10
Q

What is special about an ideal ammeter?

A

An ideal ammeter has zero resistance.

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11
Q

What is special about an ideal voltmeter?

A

An ideal voltmeter has infinite resistance.

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12
Q

Define resistivity.

A

The resistance of a 1m cylinder with CSA of 1m2

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13
Q

What effect does temperature have on the resistance of a metal conductor?

A

Increase in temperature will increase the vibrations of the ion lattice, increasing resistance.

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14
Q

What effect does temperature have on the resistance of a thermistor?

A

Increase in temperature will release more electrons from atomic bonds, descreasing resistance.

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15
Q

What is meant by ‘negative temperature coefficient?’

A

Increase in temperature decreases resistance.

These are the only type of thermistor you’ll see

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16
Q

Describe a resistance-temperature grapgh of a thermistor.

A
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17
Q

What effect does light have on the resistance of a light dependent resistor (LDR)?

A

Increase in light intentisty will release more electrons from atomic bonds, descreasing resistance.

18
Q

What is a superconductor?

A

A material with zero resistivity below a critical temperature.

Critical temperature is an inherent material property

19
Q

What is the graph of resistivity vs temperature for a superconductor?

A
20
Q

How do you add resistors in series?

A

Rtotal</sup>=R1</sup>+R2</sup>+R3</sup>+…

21
Q

How do you add resistors in parallel?

A
22
Q

What is the energy transferred to a component in time t?

A

E=IVt

23
Q

Define power.

A

Rate of energy transfer.

24
Q

What are the 3 equations for power in an electrical circuit?

A
25
Q

What is the power rating of a resistor?

A

Maximum power a resistor can withstand.

26
Q

What can be said about the current in a series circuit?

A

Current is the same everywhere in the circuit.

27
Q

What can be said about the voltages in a series circuit?

A

The sum of voltages across all components is equal to the supply p.d.

28
Q

What can be said about the current in a parallel circuit?

A

The sum of currents across all parallel set of branches is equal to the total current.

29
Q

What can be said about the voltages in a parallel circuit?

A

The potential difference across each branch is the same.

30
Q

What happens when multiple cells are connected in series?

A

The total voltage across the cells is equal to the sum of the indiviual voltages of the cells.

Vtotal</sup>=V1</sup>+V2</sup>+V3</sup>+…

31
Q

What happens when multiple identical cells are connected in parallel?

A

The total voltage is equal to the voltage of one cell.

Vtotal</sup>=V1</sup>=V2</sup>=V3</sup>=…

32
Q

What is Kirchoff’s first law?

A

Total current flowing into a junction is equal to the current flowing out of that junction.

Shows no charge is lost at any point in a circuit (charge conservation)

33
Q

What is Kirchoff’s second law?

A

Sum of all volatges in a series circuit is equal to the supply voltage.

Shows no energy is lost at any point in a circuit (energy conservation)

34
Q

What is a potential divider?

A

A circuit with at least two resistors in series connected across a voltage source.

35
Q

How does a potential divider work?

A

The potential difference being split into a ratio across the series resistors

36
Q

What is the potential divider equation?

A
37
Q

What 2 purposes are a potential dividers used for?

A

To provide a constant potential difference or to provide a variable potential difference.

38
Q

Define emf.

A

Work done in moving 1 C of charge whole way round the circuit.

39
Q

Define internal resistance.

A

Resistance inside the cell.

Electrons collide aith atoms inside cell

40
Q

Define lost volts.

A

Voltage lost due to internal resistance.

Energy wasted from electrons colliding with atoms in cell.

41
Q

Define terminal potential difference.

A

Is the emf minus the p.d. on the internal resistance.

42
Q

What is the equation for emf involving internal resistance?

A

NSFC AQA A Level Physics 12C (19 decks)

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