Electricity Flashcards

1
Q

What is the independent variable in investigating the resistance in a wire?

A

The length of the wire

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2
Q

What is the dependent variable in investigating the resistance in a wire?

A

The resistance

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3
Q

What is the control variable in investigating the resistance in a wire?

A

Type of metal or diameter of the wire

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4
Q

What is the conclusion of investigating the resistance in a wire?

A

As the length of the wire increases, the resistance of the wire also increases.

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5
Q

What is the independent variable in investigating series and parallel circuits with resistors?

A

The circuit type (series and parallel)

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6
Q

What is the dependent variable in investigating series and parallel circuits with resistors?

A

The resistance

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7
Q

What is the control variable in investigating series and parallel circuits with resistors?

A

Number of resistors, type of power source

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8
Q

What is the conclusion of investigating series and parallel circuits with resistors?

A

Adding resistors in series increases the total resistance of the circuit. In a parallel circuit, the more resistors you add, the smaller the resistance.

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9
Q

What does 1kW equal?

A

1000W

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10
Q

What does 1000W equal?

A

1kW

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11
Q

What does 0.5kW equal?

A

500W

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12
Q

What does 500W equal?

A

0.5kW

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13
Q

What is electric current?

A

The flow of electric
charge. It only flows when the circuit is complete.

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14
Q

What is charge?

A

The current flowing past a
point in a given time.

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15
Q

What is charge measured in?

A

Coulombs (C)

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16
Q

Describe an ohmic conductor.

A

The current is directly proportional to the potential difference - it is a straight line (at a constant temperature).

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17
Q

Describe a filament lamp.

A

As the current increases, so does the temperature. This makes it harder for the current to flow. The graph becomes less steep.

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18
Q

Describe a diode.

A

Current only flows in one direction. The resistance
is very high in the other direction which means no current can flow.

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19
Q

What is potential difference (voltage)?

A

The push of electrical charge.

20
Q

What does resistance do?

A

Slows down the flow of electricity.

21
Q

What does LDR stand for?

A

Light dependent resistor.

22
Q

What is an LDR dependent on.

A

Light intensity

23
Q

Describe resistance in an LDR.

A

In bright light the resistance falls and at night the resistance is higher.

24
Q

What are uses of LDR’s?

A

Outdoor night lights, burglar detectors.

25
Q

What is a thermistor?

A

A temperature dependent resistor

26
Q

Describe the resistance in a thermistor.

A

If the thermistor is hot, then the resistance is less. If the thermistor becomes cold, then the resistance increases.

27
Q

What is a use of a thermistor?

A

A thermometer (temperature detectors).

28
Q

What happens if a component is broken in a series circuit?

A

All the other components will stop working.

29
Q

Describe potential difference in a series cicuit.

A

The total p.d. of the supply is shared between all the components.

30
Q

Describe current in a series circuit.

A

Wherever the ammeter is placed in a series circuit the reading is the same.

31
Q

Describe resistance in a series circuit.

A

The resistance will add up to make the total resistance.

32
Q

Are series or parallel circuits more useful?

A

Parallel - If one component stops working it will not affect the others.

33
Q

Describe potential difference in parallel circuits.

A

The same for all components.

34
Q

Describe current in parallel circuits.

A

The total current is the total
of all the currents through all the components.

35
Q

What does adding the resistance do to parallel circuits?

A

Adding resistance reduces the total resistance.

36
Q

What is the UK mains supply?

A

230V

37
Q

What is the UK frequency?

A

50 hertz

38
Q

What is AC?

A

Alternating current - constantly changing direction.

39
Q

What is DC?

A

Direct current - Supplied by batteries and only flows in one direction.

40
Q

What are the 3 wires in cables?

A

Live, neutral and earth.

41
Q

What does the live wire do?

A

Provides the potential difference from the mains.

42
Q

What does the neutral wire do?

A

Completes the circuit.

43
Q

What is the national grid?

A

A system of cables and transformers.

44
Q

What do step - up transformers do?

A

Increase the voltage as the electricity flows through the cables.

45
Q

What do step - down transformers do?

A

Decrease the potential difference to make it safe for consumers.