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A wire of length L and 3 identical cells...

A wire of length L and 3 identical cells of negligible internal resistance are connected in series. Due to the current, the temperature of the wire is raised by `DeltaT` in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross-section but of length 2L. The temperature of the wire is raised by the same amount `DeltaT` in the same time t. the value of N is

A

4

B

5

C

8

D

6

Text Solution

Verified by Experts

The correct Answer is:
D
d. `V^2/R t = ms DeltaT`
For first case `: (3E)^2/(rhoL//A) t = ms DeltaT`
For second case: `(NE)^2/(rho2L//A) t = 2msDeltaT`.
Dividing, we get N = 6.
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