Electricity

Question 1

What is the product of current and resistance

Answer 1

A constant (so p.d won’t change)

Question 2

Explain how closing a switch would affect the current in the variable resistor

Answer 2

Current would be almost zero in the variable resistor
As the switch has effectively zero resistance

Question 3

Explain why the person could receive a fatal electric shock if the kite was very close to but not touching the power cable

Answer 3

Electric field strength is very high
Causing the air to become ionic
So the kite conducts charge to the person

Question 4

Explain why the current in the steel wire is different to the current in a single aluminium wire

Answer 4

The potential difference across the wires is the same
But the resistance of the steel wire is greater

Question 5

Explain how the resistance of a filament lamp changes as the potential difference across it increases

Answer 5

The current increases
Which causes the temperature of the filament to increase
So the resistance increases

Question 6

Explain why adding resistors on parallel decreases the total resistance

Answer 6

Multiple paths for the charge to flow
So total current is greater

Question 7

Explain why the electrician would have received an electric shock unless the circuit was disconnected from the mains supply

Answer 7

One wire in the switch is live
The electrician is earthed
So there will be a large potential difference between the live wire and the electrician