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GCSE Physics - Delete Me > 2.1 - Current, Potential Difference and Resistance > Flashcards

2.1 - Current, Potential Difference and Resistance Flashcards

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1
Q

What is required for electrical charge to flow through a closed circuit?

A

The circuit must include a source of potential difference.

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2
Q

What is electric current?

A

Electric current is a flow of electrical charge.

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3
Q

What does the size of an electric current mean?

A

The rate of flow of electrical charge (how fast the charge is flowing)

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4
Q

How are Charge flow, current and time linked?

A

Charge Flow = current × time

[Q = I × t]

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5
Q

What is the unit for Charge?

A

Coulomb ( C )

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6
Q

What symbol is normally used to represent charge in equations?

A

Q

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7
Q

What is the unit of current

A

Amperes ( A )

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8
Q

What is the symbol normally used to represent current in equations?

A

I

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9
Q

How does current change around a closed loop?

A

It doesn’t: a current has the same value at any point in a single closed loop.

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10
Q

What is the symbol for an open switch?

A

[TBC]

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11
Q

What is the symbol for a closed switch?

A

[TBC]

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12
Q

What is the symbol for a lamp?

A

[TBC]

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13
Q

What is the symbol for a fuse?

A

[TBC]

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14
Q

What is the symbol for a cell?

A

[TBC]

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15
Q

What is the symbol for a voltmeter?

A

[TBC]

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16
Q

What is the symbol for a battery?

A

[TBC]

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17
Q

What is the symbol for an ammeter?

A

[TBC]

18
Q

What is the symbol for a diode?

A

[TBC]

19
Q

What is the symbol for a thermistor?

A

[TBC]

20
Q

What is the symbol for a resistor?

A

[TBC]

21
Q

What is the symbol for a variable resistor?

A

[TBC]

22
Q

What is the symbol for an LDR?

A

[TBC]

23
Q

What is the symbol for an LED?

A

[TBC]

24
Q

What two properties of a component affect the current passing through it?

A

Resistance of the component and potential difference across it

25
Q

How are current, resistance and potential difference related for a component?

A

potential difference = current × resistance

[V = I R]

26
Q

What is the unit of potential difference?

A

Volts ( V )

27
Q

What is the symbol normally used to represent potential difference in equations?

A

V

28
Q

What is the unit of resistance?

A

Ohms ( Ω )

29
Q

What is the symbol normally used to represent resistance in equations?

A

R

30
Q

In what conditions the current passing through a component directly proportional to the potential difference across it?

A
  • If the component is ohmic
  • If the component is at constant temperature
31
Q

What is an ohmic conductor

A

A component for which the resistance stays constant for a given current and potential difference.

(A component that obeys Ohm’s law [V = IR])

32
Q

How are current and potential difference related for ohmic components?

A

Resistance is constant, so current is directly proportional to potential difference (V = IR) [Graph TBC]

33
Q

Do all components have a fixed resistance?

A

No, the resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component.

34
Q

How does the potential difference of a filament lamp change as current increases

A
  • Current increase leads to temperature increase (light turns on)
  • Temperature increase leads to resistance increase
  • Resistance increase leads to potential difference decrease (V = IR)

[Graph TBC]

35
Q

How does the potential difference of a diode change as current varies?

A
  • Diode only let current flow in one direction
  • When current is negative, resistance is very high
    • Very high resistance, so potential difference is very low (V=IR)
  • When current is positive, resistance is very low
    • Very low resistance, so potential difference is very high (V=IR)

[Graph TBC]

36
Q

What is a thermistor?

A

A component where the resistance decreases as the temperature increases

37
Q

What might a thermistor be useful for?

A

Electrical circuits which need to vary based on temperature (e.g. a thermostat)

38
Q

What is an LDR

A

Light Dependent Resistor

Resistance decreases as light intensity increases

39
Q

What might an LDR be useful for?

A

Electrical circuits which need to vary based on light (e.g. streetlamps which turn on when it gets dark)

40
Q

How can you measure the resistance of a component?

A
  • Create a circuit with the component
    • unbroken circuit
    • has a power source
  • Measure the current passing through the component
    • Ammeter
    • In series (current is the same for components in series)
  • Measure the potential difference passing through the component
    • Voltmeter
    • In parallel (potential difference is the same for components in parallel)
  • Resistance is the potential difference divided by the current (V = I R )

GCSE Physics - Delete Me (5 decks)

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