An electric heater takes a current of 4A from a 250 V supply when operating normally. How long would it take the heater to convert 400 kJ of electrical energy?
400 s
1000 s
1600 s
100 000 s
How much energy is converted in a resistor of 5.0 Ω carrying a current of 2.0 A for 10 seconds?
4.0 J
25 J
100 J
200 J
A lamp rated 6V, 2A is switched on for 60 seconds. How much energy is used?
0.2 J
20 J
180 J
720 J
The SI unit of power is Volts.
For a given electrical appliance information of “2000 W, 240 V”, it means that when an operating voltage of 240 V is applied across the appliance, the appliance converts electrical energy into thermal energy at a rate of 2000 J per minute.
1 watt is equal to 1 Joule per second
The electrical energy has a unit of joules.
To calculate the power P of any electrical appliance with a current I flowing through it and a potential difference V applied across it, we simply divide V by I.
