Question

A cylindrical conductor of length l and uniform area of cross section A has resistance R. Another conductor of length 2l and resistance R of the same material has area of cross section 

विकल्प

• A/2

• 3A/2 

• 2A 

• 3A 

Answer 1

2A 

Explanation - 

Let the resistivity of the material be ρ
Resistance (R) of the first cylindrical conductor = `(rho"l")/"A"`

where, l = length of conductor
A = area of cross section

Now, another cylindrical conductor has double length but same resistance. 
Let its area of cross section be A'

Its resistance (R') will be = `(rho xx 2"l")/"A"^"'"`

Since resistance is same

R = R'

`(rho xx "l")/"A" = (rho xx 2"l")/"A"^"'"`

Solving it, we get A' = 2A