Question

A horizontal ring of radius $$r = \frac{1}{2}m$$   is kept in a vertical constant magnetic field $$1\,T.$$  The ring is collapsed from maximum area to zero area in $$1s.$$ Then the emf induced in the ring is

A. $$1\,V$$
B. $$\left( {\frac{\pi }{4}} \right)V$$  
C. $$\left( {\frac{\pi }{2}} \right)V$$
D. $$\pi V$$
Answer :   $$\left( {\frac{\pi }{4}} \right)V$$
Solution :
$$\eqalign{ & \left| e \right| = B\frac{{dA}}{{dt}} \cr & \left| e \right| = B\frac{{\left( {{A_2} - {A_1}} \right)}}{{\left( {{t_2} - {t_1}} \right)}} \cr & \Rightarrow \left| e \right| = \frac{{1\left( {\frac{\pi }{4} - 0} \right)}}{{\left( {1 - 0} \right)}} \cr & e = \frac{\pi }{4}V \cr} $$

Releted MCQ Question on
Electrostatics and Magnetism >> Electromagnetic Induction

Releted Question 1

A thin circular ring of area $$A$$ is held perpendicular to a uniform magnetic field of induction $$B.$$ $$A$$ small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is $$R.$$ When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is

A. $$\frac{{BR}}{A}$$
B. $$\frac{{AB}}{R}$$
C. $$ABR$$
D. $$\frac{{{B^2}A}}{{{R^2}}}$$
Releted Question 2

A thin semi-circular conducting ring of radius $$R$$ is falling with its plane vertical in horizontal magnetic induction $$\overrightarrow B .$$  At the position $$MNQ$$  the speed of the ring is $$v,$$ and the potential difference developed across the ring is
Electromagnetic Induction mcq question image

A. zero
B. $$\frac{{Bv\pi {R^2}}}{2}$$  and $$M$$ is at higher potential
C. $$\pi RBv$$  and $$Q$$ is at higher potential
D. $$2RBv$$  and $$Q$$ is at higher potential
Releted Question 3

Two identical circular loops of metal wire are lying on a table without touching each other. Loop-$$A$$ carries a current which increases with time. In response, the loop-$$B$$

A. remains stationary
B. is attracted by the loop-$$A$$
C. is repelled by the loop-$$A$$
D. rotates about its $$CM,$$  with $$CM$$  fixed
Releted Question 4

A coil of inductance $$8.4 mH$$  and resistance $$6\,\Omega $$  is connected to a $$12 V$$  battery. The current in the coil is $$1.0 A$$  at approximately the time

A. $$500 s$$
B. $$25 s$$
C. $$35 ms$$
D. $$1 ms$$

Practice More Releted MCQ Question on
Electromagnetic Induction


Practice More MCQ Question on Physics Section