Electricity

Question 1

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

Answer 1

The length of the wire

Question 2

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

Answer 2

The resistance

Question 3

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

Answer 3

Type of metal or diameter of the wire

Question 4

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

Answer 4

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

Question 5

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

Answer 5

The circuit type (series and parallel)

Question 6

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

Answer 6

The resistance

Question 7

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

Answer 7

Number of resistors, type of power source

Question 8

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

Answer 8

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

Question 9

What does 1kW equal?

Answer 9

1000W

Question 10

What does 1000W equal?

Answer 10

1kW

Question 11

What does 0.5kW equal?

Answer 11

500W

Question 12

What does 500W equal?

Answer 12

0.5kW

Question 13

What is electric current?

Answer 13

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

Question 14

What is charge?

Answer 14

The current flowing past a
point in a given time.

Question 15

What is charge measured in?

Answer 15

Coulombs (C)

Question 16

Describe an ohmic conductor.

Answer 16

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

Question 17

Describe a filament lamp.

Answer 17

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

Question 18

Describe a diode.

Answer 18

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

Question 19

What is potential difference (voltage)?

Answer 19

The push of electrical charge.

Question 20

What does resistance do?

Answer 20

Slows down the flow of electricity.

Question 21

What does LDR stand for?

Answer 21

Light dependent resistor.

Question 22

What is an LDR dependent on.

Answer 22

Light intensity

Question 23

Describe resistance in an LDR.

Answer 23

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

Question 24

What are uses of LDR’s?

Answer 24

Outdoor night lights, burglar detectors.

Question 25

What is a thermistor?

Answer 25

A temperature dependent resistor

Question 26

Describe the resistance in a thermistor.

Answer 26

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

Question 27

What is a use of a thermistor?

Answer 27

A thermometer (temperature detectors).

Question 28

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

Answer 28

All the other components will stop working.

Question 29

Describe potential difference in a series cicuit.

Answer 29

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

Question 30

Describe current in a series circuit.

Answer 30

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

Question 31

Describe resistance in a series circuit.

Answer 31

The resistance will add up to make the total resistance.

Question 32

Are series or parallel circuits more useful?

Answer 32

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

Question 33

Describe potential difference in parallel circuits.

Answer 33

The same for all components.

Question 34

Describe current in parallel circuits.

Answer 34

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

Question 35

What does adding the resistance do to parallel circuits?

Answer 35

Adding resistance reduces the total resistance.

Question 36

What is the UK mains supply?

Answer 36

230V

Question 37

What is the UK frequency?

Answer 37

50 hertz

Question 38

What is AC?

Answer 38

Alternating current - constantly changing direction.

Question 39

What is DC?

Answer 39

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

Question 40

What are the 3 wires in cables?

Answer 40

Live, neutral and earth.

Question 41

What does the live wire do?

Answer 41

Provides the potential difference from the mains.

Question 42

What does the neutral wire do?

Answer 42

Completes the circuit.

Question 43

What is the national grid?

Answer 43

A system of cables and transformers.

Question 44

What do step - up transformers do?

Answer 44

Increase the voltage as the electricity flows through the cables.

Question 45

What do step - down transformers do?

Answer 45

Decrease the potential difference to make it safe for consumers.