Heat Transfer

The heat required to raise the temperature of the water is given by the formula: where: - (since 2 litres of water is 2 kg) - (specific heat of water) - Thus, the heat required is: The power supplied by the coil is 1 kW, i.e., .
However, the energy is dissipating at a rate of 160 J/s, so the effective power heating the water is: Now, the time required to heat the water is:
Thus, the correct answer is (b).