Power and Energy

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?

How much energy is converted in a resistor of 5.0 Ω carrying a current of 2.0 A for 10 seconds?

A lamp rated 6V, 2A is switched on for 60 seconds. How much energy is used?

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.