Question

# A current ( I=1.5 ) A is flowing through a long solenoid of diameter ( 3.2 mathrm{cm}, ) having 220 turns per cm. At its centre, a 130 turn closely packed coil of diameter ( 2.1 mathrm{cm} ) is placed such that the coil is coaxial with the long solenoid. The current in the solenoid is reduced to zero at a steady rate in 25 ms. What is the magnitude of emf induced in the coil while the current in the solenoid is changing?

Solution

field throught he inner solenoid ( n=22000 ) tur ( n / m i=1.5 )

( B=mu_{0} n i=4 pi^{*} 10^{-7} * 22000^{*} 1.5=0 )

0415 tesla

emf induced in the coil ( =frac{130^{*} 0.0415^{*} pi^{*}(0.0105)^{2}}{25^{*} 10^{-3}}=0.0748 mathrm{Volt} )