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Que. An electric cable of aluminum (k = 240 W/ m degree) is to be insulated with rubber (k = 6 W/ square meter degree). If the cable is in air (h = 6 W/square meter degree). Find the critical radius?
a. 80 mm
b. 160 mm
c. 40 mm
d. 25 mm
Correct Answer:25 mm
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