Question

A circular loop of radius r is made of a wire of circular cross section of diameter ‘a’. When current I flows through the loop the magnetic flux linked with the loop due to self induced magnetic field is given by `phi = mu_(0)r [ln((16r)/(a)) - (7)/(4)]l`. The resistivity of the material of teh wire is `rho` and `r gt gt a`.Switch S is closed at time `t = 0` so as to connect the loop to a cell of emf `V`. Find the current in the loop at time t.

Answer 1

Correct Answer - `i = (Va^(2))/(8 rho r) [1- e^(-t//tau)]`
Where `tau = (mu_(0)a^(2))/(8rho) [In ((16r)/(a)) - (7)/(4)]`