Physics

Problem

A heating coil of resistance

20\,\Omega

is connected to a

230\,\text{V}

supply and used to heat

500\,\text{g}

of water from

20^{\circ}\text{C}

80^{\circ}\text{C}

. The specific heat capacity of water is

4.2\,\text{kJ}\,\text{kg}^{-1}\,{}^{\circ}\text{C}^{-1}

. Assume that

85\%

of the electrical energy supplied is absorbed by the water. a. (a) Calculate the thermal energy absorbed by the water. b. (b) Find the time for which the coil must be switched on to achieve the required temperature rise.

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