Question

Two infinitely long parallel wires having linear charge densities `lambda_(1)` and `lambda_(2)` respectively are placed at a distance of `R` metres. The force per unit length on either wire will be `(k= 1/(4piepsilon_(0)))`
A. `k(2lambda_(1)lambda_(2))/(R^(2))`
B. `k(2lambda_(1)lambda_(2))/(R)`
C. `k(lambda_(1)lambda_(2))/(R^(2))`
D. `k(lambda_(1)lambda_(2))/(R)`

Answer 1

Correct Answer - b
Force on `l` length of the wire `2` is
`F_(2)=QE_(1)= (lambda_(2)l)(2klambda_(1))/(R)`
`implies (F_(2))/(l)=(2klambda_(1)lambda_(2))/(R)`
Also `(F_(1))/(l)=(F_(2))/(l)=(F)/(l)=(2klambda_(1)lambda_(2))/(R)`