Question

A magnetic field of flux density 1.0 Wb $m^{-2}$ acts normal to a 80 tum coil of 0.01 $m^2$ area. The e.m.f. induced in it, if this coil is removed from the field in 0.1 second is :

• A. 8V
• B. 4V
• C. 10V
• D. 6V

Answer 1

The correct option is A 8V

Answer is A.
The magnetic flux $\varphi =B\times A$ depends on the magnetic field, the area of the loop, and their relative orientation.
In this case, the magnetic field of flux density $1.0Wb{m}^{-2}$ acts normal to a 80 turns coil of $0.01m^2$ area.
Therefore, the Magnetic flux in 80 turns of coil = 0.01 * 80 = 0.8 T.
The time derivative of the flux is given as, d$\varphi$/dt.
Therefore, the e.m.f induced in it, if this coil is removed from the field in 0.1 second is d$\varphi$/dt = 0.8/0.1 = 8 V.
The e.m.f induced is 8 V.