An air-conditioning unit, a lamp and an electric fire all receive electrical energy from the mains supply.
From which of these devices is all this energy eventually transferred to the surroundings?
airconditioning unit
air-
conditioning
unit
lamp
electric
fire
✓
✓
✓
✓
χ
✓
×
✓
✓
χ
×
✓
key
✓ = all energy transferred to surroundings
x= not all energy transferred to surroundings
A
A water heater is connected to a 230 V supply and there is a current of 26 A in the heater.
It takes 20 minutes to heat the water to the required temperature.
How much energy is supplied by the heater?
6.0×103 J
1.0×104 J
1.2×105 J
7.2×106 J
D
The cost of electrical energy is $ 0.25 for each unit of 1 kWh. A 2200 W heater is switched on for 48 minutes.
What is the cost of this use?
$ 0.44
$ 0.55
$ 26
$ 440
A