A steel sphere of radius 0 1 m at 400 K...

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A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.

A. 5 minutes

B. 10 minutes

C. 20 minutes

D. 40 minutes

Answer: Option A

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