ELECTRICITY

Question 1

Why is the current provided by a cell call direct current

Answer 1

Only flows in one direction

Question 2

What is alternating current

Answer 2

Current that repeatedly reverses direction

Question 3

What is the frequency and voltage of mains electricity

Answer 3

50Hz, 230V

Question 4

What kind of current is supplied by mains electricity

Answer 4

Alternating current

Question 5

What colours are the live, neutral and earth wires in a three core cable

Answer 5

Live - brown
Neutral - blue
Earth - green and yellow

Question 6

What is the function of the live wire in a cable

Answer 6

Carries the alternating potential difference from the supply

Question 7

What is the function of the neutral wire

Answer 7

Completes the circuit

Question 8

What is the function of the earth wire

Answer 8

safety wire to stop the appliance becoming live

Question 9

When is there current in the earth wire

Answer 9

When there’s a fault

Question 10

Why is the live wire dangerous

Answer 10

Provides a large p.d that would cause a large current to flow through a person if they touched it

Question 11

What is the national grid

Answer 11

nationwide network of cables and transformers that link power stations to customers

Question 12

What are the step up transformers used for in the national grid

Answer 12

increase the p.d from the power station so that less current is needed to transfer the name amount of power so that less power is wasted due to heating

Question 13

What two things does energy transfer to an appliance depend on

Answer 13

Power of appliance and time its switched on for

Question 14

How does a material become charged

Answer 14

Gaining or losing electrons

Question 15

What will two objects carrying the same type of charge do if they are brought close to each other

Answer 15

Repel each other

Question 16

What happens to the strength of an electric field as. you get further from the charged object

Answer 16

It decreases

Question 17

What is an electric current

Answer 17

Rate of flow of charge

Question 18

What is the same at all points when charge flows in a closed loop

Answer 18

current

Question 19

What must there be in a closed circuit so that electrical charge can flow

Answer 19

Potential difference

Question 20

Which 2 factors does current depend on and what are their units

Answer 20

Resistance in ohms and p.d in volts

Question 21

What happens to the current is the resistance is increased but the p.d stays the same

Answer 21

current decreases

Question 22

what is an ohmic conductor

Answer 22

conductor where the current is directly proportional to the voltage so resistance is constant

Question 23

what happens to the resistance of a filament lamp as its temperature increases

Answer 23

increases

Question 24

what happens to the resistance of a thermistor as its temperature increases

Answer 24

decreases

Question 25

what happens to the resistance of a light dependant resistor as its temperature increases

Answer 25

decreases

Question 26

main features of a series circuit

Answer 26

• same current each component
• total p.d of power supply is shared between components
• total resistance of all components is the sum of the resistance of each component

Question 27

main features of a parallel circuit

Answer 27

• pd across each branch is the same
• total current is the sum of currents in each branch
• total resistance of all resistors is less than the resistance of the smallest individual resistor