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Two rods are of same material and having...

Two rods are of same material and having same length and area. If heat `DeltaQ` flows through them for 12 min when they are joined side by side. If now both the rods are joined in parallel, then the same amount of heat `DeltaQ` will flow in

A

24 min

B

3 min

C

12 min

D

6 min

Text Solution

Verified by Experts

The correct Answer is:
B
Let R = thermal resistance of each rod.
In first case, `R_("net") = R + R = 2R` (in series)
In second case, `R_("net") = R/2` (in parallel)
In second case thermal resistance has become `1/4 th.`
So, heat current will become 4 times. So time
taken to flow same amount of heat will be reduced
to `1/4th`.
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