A 40 mm diameter electric cable of an Aluminium conductor of thermal conductivity 240 W/mK is to be insulated with rubber of thermal conductivity 0.15 W/mK. The cable is to be located in the air with a heat transfer coefficient of 6 W/m2K. The critical thickness of insulation will be

A 40 mm diameter electric cable of an Aluminium conductor of thermal

1.	A 40 mm diameter electric cable of an Aluminium conductor of thermal conductivity 240 W/mK is to be insulated with rubber of thermal conductivity 0.15 W/mK. The cable is to be located in the air with a heat transfer coefficient of 6 W/m2K. The critical thickness of insulation will be
A.	5 mm
B.	25 mm
C.	20 mm
D.	15 mm
Answer» B. 25 mm

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A 40 mm diameter electric cable of an Aluminium conductor of thermal conductivity 240 W/mK is to be insulated with rubber of thermal conductivity 0.15 W/mK. The cable is to be located in the air with a heat transfer coefficient of 6 W/m2K. The critical thickness of insulation will be

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