Practice Questions

1. An appliance transfers 200J of energy and a charge flows of 600mC. Calculate the potential difference that the appliance has. 

600mC = 0.6C

Energy = Potential difference x charge flow

E = V x Q

V = E/Q

V = 200/0.6

V = 33v

2. A mobile phone charger will supply 450J over 1.5 minutes. Calculate the power of the mobile phone charger

1.5 minutes = 90 seconds

Power = energy/time

Power = 450/90

Power = 5W

3. Calculate the energy transferred when a potential difference of 0.25kv is applied over a time period of 4 minutes using a current of 10A.

Energy = Potential difference x current x time

E = vIt

0.25kv = 250v

4 minutes = 240 seconds

E = 250 x 10 x 240 = 600000J