A conducting circular loop is placed is a uniform magnetic field B =0.20 T with its plane perpendicualr to the field . Somehow, the radius of the loop starts shrinking at a constant rate of `1.0 mm s^(-1)`. Find the induced emf in the loop at an instant when the radius is 2 cm.

Explanation

Here, `theta = (960)/(16) = 60 km//h = 16.67 m//s`.
Field intercepted, `B = 4 xx 10^(-5) T`,
`l = 130 cm = 1.3 m`
Average e.m.f. induced, `e = B upsilon l`
` = 4 xx 10^(-5) xx 16.67 xx 1.3`
`= 8.6 xx 10^(-4) V`
Leakage current, `i = (e)/(R ) = (8.6 xx 10^(-4))/(100)`
`= 8.6 xx 10^(-6) A`
`:.` Retarding force, `F = B i l`
`= (4 xx 10^(-5)) xx (8.6 xx 10^(-6)) xx 1.3`
`F = 4.47 xx 10^(-10) N`