1. 2 million kettles at 3kW each = 6GW
Mains filament lamp
10,000 W cooker
2 million kettles at 3kW each = 6GW
P= E so E = Pt t
E = 5000W x 20s
E = 100,000 J
% efficiency = OP energy x 100%
IP energy
= 12, x 100%
100,000
= 12%

2. a. P = E t
P = 1,500,000 J s
P = 1,500, W 50
P = 30,000 W
P = kW b.
% efficiency = OP power x 100%
IP power
= 30kW x 100%
100kW
= %

3. P= E so E = Pt t E = 12 kW x (20 x60 x4 ) s E = 12 k W x 4800 s
E = 57,600 kJ
E = MJ
Increase in the thermal energy store
of the water
Electric
Current in the wires
Increase in the thermal energy store of the surroundings.
Caused by the
heating from
the hot shower heater
( less than 1% )