+Electrical power and energy

When a direct current of I amperes is flowing in an electric circuit and

the voltage across the circuit is V volts, then

 Electrical energy      = Power x 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 x 3600 watt seconds or joules

                                 = 3 600 000 J

Energy                       = power x time and power 
                                  = voltage x current. Hence

Energy                       = VIt
                                  = 5 x 3 x 10 x 60

                                  = 9000 Ws or J                                
                                  = 9 kJ