A heating coil of resistance is connected to a supply and used to heat of water from to

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

Problem

A heating coil of resistance 20 Ω20\,\Omega is connected to a 230 V230\,\text{V} supply and used to heat 500 g500\,\text{g} of water from 20∘C20^{\circ}\text{C} to 80∘C80^{\circ}\text{C}. The specific heat capacity of water is 4.2 kJ kg−1 ∘C−14.2\,\text{kJ}\,\text{kg}^{-1}\,{}^{\circ}\text{C}^{-1}. Assume that 85%85\% of the electrical energy supplied is absorbed by the water. (a) Calculate the thermal energy absorbed by the water. (b) Find the time for which the coil must be switched on to achieve the required temperature rise.

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