MCQ
A metallic ring is dropped down, keeping its plane perpendicular to a constant and horizontal magnetic field. The ring enters the region of magnetic field at $t = 0$ and completely emerges out at $t = T\,sec$. The current in the ring varies as
  • A


  • C

  • D

Answer

Correct option: B.

b
When ring enters the field an $emf$ is induced due to change in flux. Once with the magnetic field, there is no change in flux in the ring so there is no $emf$. When it emerges out of the field, once again there is a flux change which creates $emf$ in reverse direction. Graph $(b)$ shows this result.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

Water is filled in a container upto height of $3\,m$. A small hole of area $‘A_0’$ is punched in the wall of the container at a height $52.5\, cm$ from the bottom. The cross sectional area of the container is $A$. If $A_0/A = 0.1$ then $v^2$ is......... $m^2/s^2$ (where $v$ is the velocity of water coming out of the hole)
A particle moves along $X-$axis as $x = 4(t - 2) + a{(t - 2)^2}$ Which of the following is true ?
A point particle of mass $0.1\, kg$ is executing $S.H.M$. of amplitude of $0.1\, m$. When the particle passes through the mean position, its kinetic energy is $8\times10^{-3}$ Joule. Obtain the equation of motion of this particle if this initial phase of oscillation is $45^o$.
A body with mass $2\, kg$ moves in one direction in the presence of a force which is described by the potential energy graph. If the body is released from rest at $x = 2m$, then its speed when it crosses $x = 5\, m$ is ................ $\mathrm{m}/ \mathrm{s}$
The displacement of a damped harmonic oscillator is given by $x\left( t \right) = {e^{ - 0.1\,t}}\,\cos \left( {10\pi t + \varphi } \right)$  The time taken for its amplitude of vibration to drop to half of its initial value is close to .... $s$
The length of a potentiometer wire is $\ell $.  A cell of emf $E$ is balanced at a length $\ell /3$  from the positive end of the wire. If the length of the wire is increased by $\ell /2$ at what distance will the same cell give a balanced point
From the following $V-T$ diagram we can conclude
As the $n$ (number of orbit) increases, the difference of energy between the consecutive energy levels
A uniform beam of weight $W$ is attached to a vertical wall by a hinge $H$ . The beam is held horizontal by a rope as shown below. Which one of the following best shows the direction of the reaction force $R$ at the hinge ?
Given below are two statement : one is labelled as Assertion $A$ and the other is labelled as Reason $R$.

Assertion $A$ : When a rod lying freely is heated, no thermal stress is developed in it.

Reason $R :$ On heating the length of the rod increases.

In the light of the above statements, choose the correct answer from the options given below