When a potential difference of 10 V is applied to a coil of copper wire of mean temperature 20 °C, a current of 1.0 A flows in the coil. After some time the current falls to 0.95 A yet the supply voltage remains unaltered.
Determine the mean temperature of the coil given that the temperature coefficient of resistance of copper is 4.28 x 10-3 °C referred to 0 °C.