Two litres of water (density = 1 g/ml) in an open lid insulated kettle is heated by an electric heater of power 1 kW. The heat is lost from the lid at the rate of 160 J/s. The time taken for heating water (specific heat capacity ) from 20°C to 75°C is ___seconds.
Mass of 2 litres of water = 2 kg. Heat energy needed to raise the temperature of2 kg of water from 20°C to 75°C is
If t is the time taken, heat energy supplied by the heater in time t is
Heat energy lost in time t is
Heat energy available for heating water is
Equating , we get .