When a direct current of I amperes is flowing in an electric circuit and the voltage across the circuit is V volts, then

power, in watts P =VI
Electrical energy = Power × time
= VIt joules

Although the unit of energy is the joule, when dealing with large amounts of energy, the unit used is the kilowatt hour (kWh) where

1 kWh = 1000 watt hour
= 1000 × 3600 watt seconds or joules
= 3 600 000 J

[sc_fs_faq html=”true” headline=”h2″ img=”” question=”A source e.m.f of 5V supplies a current of 3A for 10 minutes. How much energy is provided in this time?” img_alt=”” css_class=””] Energy = power × time, and power = voltage × current. Hence
<b>Energy</b> = VIt = 5 × 3 × (10 × 60) <br> = 9000 Ws or J = 9 kJ [/sc_fs_faq]