P1: Electricity

Question 1

What is a switch?

Answer 1

Something that is used to turn a circuit on and off.

Question 2

What is a lamp?

Answer 2

An electrical current heats the filament on a bulb so that it gives out light.

Question 3

What is a fixed resistor?

Answer 3

A restistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that does not change.

Question 4

What is a variable resistor?

Answer 4

A resistor whereby the resistance can be changed.

Question 5

What is a thermistor?

Answer 5

A resistor whereby the resistance changes depending on the temperature.

Question 6

At low temperatures, what is the resistance like in a thermistor?

Answer 6

High.

Question 7

Does resistance in a thermistor increase or decrease with temperature increase?

Answer 7

Resistance decreases.

Question 8

What is a light-dependent resistor?

Answer 8

A resistor whereby the resistance depends on light intensity. At low light levels, the LDR has a high resistance.

Question 9

In the dark, is the resistance of an LDR high or low?

Answer 9

High.

Question 10

Does resistance in an LDR increase or decrease as light increases?

Answer 10

Resistance decreases.

Question 11

What is a diode?

Answer 11

Something that allows current to flow in one direction early. Used to convert an alternating current into a direct current.

Question 12

What is current?

Answer 12

The rate of flow of electric charge.

Question 13

What is charge?

Answer 13

The quantity of electricity.

Question 14

How is current measured?

Answer 14

Using an ammeter.

Question 15

How is an ammeter placed in a circuit?

Answer 15

In series.

Question 16

What do you use to measure potential difference?

Answer 16

A voltmeter.

Question 17

How do you place a voltmeter in a circuit?

Answer 17

In parallel.

Question 18

Describe the layout of electrical components in a series circuit.

Answer 18

They are connected one after the other in a single loop.

Question 19

What happens if one bulb goes out in a series circuit?

Answer 19

All of the other bulbs go out as well because current is not able to flow around the circuit.

Question 20

Describe current in a series circuit.

Answer 20

Current is the same everywhere in a series circuit.

Question 21

Describe the distribution of potential difference in a series circuit.

Answer 21

The potential different in each component is equal across all of them, and adds up to the total potential difference in the source.

Question 22

Describe the resistance of a series circuit.

Answer 22

The total resistance of the circuit is the sum of individual resistors.

Question 23

What happens if one bulb is broken in a parallel circuit?

Answer 23

The current will still be able to flow through the other loops, so all of the others will stay on.

Question 24

Describe the current in a parallel circuit.

Answer 24

The total current is split between the components on different loops.

Question 25

Describe the potential difference in a parallel circuit.

Answer 25

The potential difference is the same across each loop, everywhere.

Question 26

Describe the resistance in a parallel circuit.

Answer 26

The total resistance of the circuit is less than the resistance of the smallest resistor.

Question 27

What are the types of ways a current can flow?

Answer 27

Direct current and alternating current.

Question 28

What are the three types of wire in a plug?

Answer 28

Earth wire, neutral wire and live wire.

Question 29

What is the function of outer insulation in a plug?

Answer 29

Safety.

Question 30

What is the function of a cable grip in a plug?

Answer 30

Holds the cable tightly in place so that wires do not become loose,

Question 31

What is the function of a fuse in a plug?

Answer 31

Melts if the current gets too high, protects from excessive current and prevents short circuits.

Question 32

What colour is the live wire?

Answer 32

Brown.

Question 33

What colour is the neutral wire?

Answer 33

Blue.

Question 34

What colour is the Earth wire?

Answer 34

Yellow and green.

Question 35

Which wire in a plug is brown?

Answer 35

Live wire.

Question 36

Which wire in a plug is blue?

Answer 36

Neutral wire.

Question 37

Which wire in a plug is green and yellow?

Answer 37

Earth wire.

Question 38

What is the function of the live wire in a plug?

Answer 38

Allows the current to enter the plug.

Question 39

What is the function of a neutral wire in a plug?

Answer 39

Connects to the cable in the wall and completes the circuit.

Question 40

What is the purpose of the Earth wire in a plug?

Answer 40

Provides a path for current to flow from the case of the device to the ground if there is a fault.

Question 41

What would happen if a fault occurred making the live wire loose, and there was no Earth wire?

Answer 41

The live wire could touch the case, and the next person who uses the appliance would get electrocuted.

Question 42

Describe the steps in the National Grid.

Answer 42

Power station —> Step-up transformers —> High voltage transmission lines —> Step-down transformers —> Consumers

Question 43

What does the National Grid do?

Answer 43

Distributed electricity across the country.

Question 44

What does a step-up transformer do?

Answer 44

Increases the voltage from 25,000 volts to 400,000 volts.

Question 45

What does a step-down transformer do?

Answer 45

Decreases the voltage from 400,000 Volts to 230 Volts for home usage.

Question 46

What is done to the cables in transmission lines to reduce power loss?

Answer 46

-The cables are thick to reduce resistance -High voltages are used to reduce the current

Question 47

How can objects that are charged affect other charged objects?

Answer 47

By using the non-contact forces of static electricity.

Question 48

What is the charge of an electron?

Answer 48

-1

Question 49

What may happen when insulating material rub against each other?

Answer 49

They may become electrically charged. Electrons will be rubbed off one material and on to the other.

Question 50

What force gives electrons enough energy to leave the atom and be rubbed off an object?

Answer 50

Friction.

Question 51

What keeps charge static?

Answer 51

If the electrons can’t move.

Question 52

What do all charged objects have?

Answer 52

An electric field around them.

Question 53

What does a Van de Graaff generator do?

Answer 53

Removes electrons to produce a positive charge.

Question 54

What happens to a charge if an electric field is strong enough?

Answer 54

Charges can be forced through insulators such as air and a spark will occur. (This is what happens during a lightning strike)