A cylindrical conductor of length l and unifor

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Solution

Q.
A cylindrical conductor of length l and uniform area of cross-section A has resistance R. The area of cross-section of another conductor of same material and same resistance but of length 2l is:

1 0.5 A

2 1.5 A

3 2 A

4 3 A

Ans.
(3)

For a conductor, $R = ρ \frac{l}{A}$

$\frac{R_{1}}{R_{2}} = (\frac{L_{1}}{L_{2}}) \times (\frac{A_{2}}{A_{1}}) A_{2} = (\frac{R_{1}}{R_{2}}) \times (\frac{L_{2}}{L_{1}}) A_{1} A_{2} = (\frac{R}{R}) \times (\frac{2 l}{l}) A A_{2} = 2 A$

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