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Conduction

If the radius...

Question

If the radius and length of a copper rod are doubled, the rate of heat flowing along the rod increases to :

A

4 times

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B

2 times

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C

8 times

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D

16 times

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Solution

The correct option is B 2 times
We know that: $Q = \frac{K A Δ T}{l}$
$Q \propto \frac{A}{l}$
So, $\frac{A_{1}}{l_{1}} = 2 \frac{A_{2}}{l_{2}}$
So, we know that $Q \propto \frac{A}{l}$
Hence, it will increase by 2 times.

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