Given:

Resistance of the loop R=4.5mΩ

Time interval=30s

As heat produced is a scalar quantity total heat is found by algebraically adding heat produced in different time intervals

Where

heat produced during time interval 0-5s

heat produced during time interval 5-20s

heat produced during time interval 20-25s

heat produced during time interval 25-30s

Now,

(i) during time interval 0-5s emf produced in the loop is given by

Current in the coil is

Heat produced in the coil is given by the formula

…. (i)

where

i=current

R=resistance

t=time interval

putting the values of i, R and t in above eqn. we get,

Emf induced in the time interval 5-20s and 25-30s =0

So current in the coil during this time

Heat produced in the coil is given by eqn.(i)

Emf induced in the time interval 20-25s is same as that induced at 5s

Hence the current and heat produced during this interval is same and given by

Total heat produced is given by

Therefore total heat produced in the loop during interval 0-30s is