An electric kettle contains a heating coil of resistance

PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity

Problem

55\,\Omega

. The kettle holds

1.0\,\text{kg}

of water at

20^{\circ}\text{C}

and the kettle itself (including the coil) has a heat capacity of

420\,\text{J}^{\circ}\text{C}^{-1}

. The kettle is connected to a

230\,\text{V}

mains supply. If

80\%

of the electrical energy supplied is actually used to heat the water and the kettle (the rest is lost to the surroundings), answer the following: (i) Calculate the electrical energy supplied by the kettle in

1\,\text{min}

of operation. (ii) Determine the total heat required to raise the temperature of the water from

20^{\circ}\text{C}

to its boiling point at

100^{\circ}\text{C}

, taking the specific heat capacity of water as

4.2\times10^{3}\,\text{J kg}^{-1}\!{}^{\circ}\text{C}^{-1}

. (iii) Using your answers from parts (i) and (ii), estimate the time required for the water to reach its boiling point.

Related theory

Browse the problem library