Two bars of equal resistivity `rho` and radius 'r' and '2r' are kept in contact as show. An electric current is passed through the bars. Which one of the following is correct ?

Options

A. Heat produced in bar BC is 4 times the heat produced in bar AB
B. Electric field in both halves is equal
C. Current density across AB is double that of across BC
D. Potential difference across AB is 4 times that of across BC

Explanation

Current flowing through both the bars is equal. Now the heat produced is given by `H=I^2Rt or H prop R`
or `H_(AB)/H_(BC)=R_(AB)/R_(BC)=(1//2r)^2/(1//r)^2 (as R prop 1/2 prop 1/r^2)=1//4 or H_(BC)=4H_(AB)`