Question

A cylindrical conductor of length 'l' and uniform area of the cross section a has resistance are another conductor of length 2.5 l and resistance 0.5 are of the same material has area of cross section
A.5a
B.2.5a
C.O.5a
D.1/5a

Answer 1

Answer:

and your answer is c 0.5 a

Answer 2

The area of the cross section of the material is 5 times of the initial area.

Explanation:

A cylindrical conductor of length l and uniform area of cross-section A  has resistance R. The resistance of the conductor is given by :

$R=\rho\dfrac{l}{A}$...........(1)

Another conductor of length 2.5 l and resistance 0.5 R  of the same material. New resistance is given by :

$0.5R=\rho\dfrac{2.5l}{A'}$........(2)

Dividing equation (1) and (2). We get :

$\dfrac{R}{0.5R}=\dfrac{(l/A)}{(2.5l/A')}\\\\2=\dfrac{2A'}{5A}\\\\A'=5A$

So, the area of the cross section of the material is 5 times of the initial area. Hence, the correct option is (A).

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