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Q20. A wire of diameter 2 mm carries an electric current, and each metre length generates 2 watts of heat. The surrounding air is at 25°C and the surface heat transfer coefficient is 10 W/m²K.

(a) Determine the temperature of the wire. (5)

(b) Determine the new temperature of the wire if it is to be covered with insulation 1 mm thick and of thermal conductivity 0.1 W/mK. The heat transfer coefficient at the outer surface may be assumed to remain the same. (6)

(c) Command on the values of temperature obtained in Q7(a) and Q7(b). (5)