## Important Questions on Electromagnetic Induction

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A metal disc of radius $100\mathrm{cm}$ is rotated at a constant angular speed of $60\mathrm{rad}{\mathrm{s}}^{-1}$ in a plane at right angles to an external field of magnetic induction $0.05\mathrm{Wb}{\mathrm{m}}^{-2}$. The emf induced between the centre and a point on the rim will be

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A $800$ turn coil of the effective area $0.05\text{\hspace{0.17em}\hspace{0.17em}}{\mathrm{m}}^{2}$ is kept perpendicular to the magnetic field $5\times {10}^{-5}\text{\hspace{0.17em}\hspace{0.17em}}\mathrm{T}.$When the plane of the coil is rotated by ${90}^{\mathrm{o}}$ around any of its coplanar axis in $0.1\mathrm{s},$ the emf induced in the coil will be:

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

At time $t=0$ magnetic field of $1000\mathrm{G}\mathrm{a}\mathrm{u}\mathrm{s}\mathrm{s}$ is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to $500\mathrm{G}\mathrm{a}\mathrm{u}\mathrm{s}\mathrm{s},$ in the next $5\mathrm{s},$ then induced $\mathrm{E}\mathrm{M}\mathrm{F}$ in the loop is:

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer $\text{G}$ attached across the coil?

Three positions shown describe: (a) the magnet's entry (b) magnet is completely inside and (c) magnet's exit.MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A uniform magnetic field is restricted within a region of radius,$r.$ The magnetic field changes with time at a rate,$\frac{d\overrightarrow{B}}{dt}$. Loop one of radius $R>r$ encloses the region, $r$ and loop two of radius, $R$ is outside the region of magnetic field as shown in the figure below. Then the emf generated is

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A planar loop of wire rotates in a uniform magnetic field. Initially, at $t=0$ , the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of $10\mathrm{s}$ about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at:

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A very long solenoid of radius $\mathrm{R}$ is carrying current $\mathrm{I}\left(\mathrm{t}\right)=\mathrm{k}\mathrm{t}{\mathrm{e}}^{-\mathrm{\alpha}\mathrm{t}}\left(\mathrm{k}>0\right),$ as a function of time $\left(\mathrm{t}\ge 0\right).$ Counterclockwise current is taken to be positive. A circular conducting coil of radius $2\mathrm{R}$ is placed in the equitorial plane of the solenoid and concentric with the solenoid. The current induced in the outer coil is correctly depicted, as a function of time, by:

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

The magnetic flux through a coil varies with time as $\mathrm{\varphi}=5{t}^{2}+6t+9$. The ratio of emfat $t=3\mathrm{s}$ to $\mathrm{t}=0\mathrm{s}$will be

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

The figure shows a bar magnet and a metallic coil. Consider four situations. (I) Moving the magnet away from the coil. (II) Moving the coil towards the magnet. (III) Rotating the coil about the vertical diameter. (IV) Rotating the coil about its axis.

An emf in the coil will be generated for the following situations.

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A long solenoid of diameter $0.1\mathrm{m}$ has $2\times {10}^{4}$ turns per meter. At the centre of the solenoid, a coil of $100$ turns and radius $0.01\mathrm{m}$ is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to $0\mathrm{A}$ from $4\mathrm{A}$ in $0.05\mathrm{s}$. If the resistance of the coil is $10{\mathrm{\pi}}^{2}\Omega ,$ the total charge flowing through the coil during this time is

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc, the disc will (figure is schematic and not drawn to scale)

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A conducting square frame of side $\text{a}$ and a long straight wire carrying current $\text{I}$ are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity $\text{V}$. The e.m.f induced in the frame (when the centre of the frame is at a distance$x$ from the wire) will be proportional to :

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

The magnetic flux linked with a coil (in $\mathrm{Wb}$) is given by the equation $\varphi =5{t}^{2}+3t+16$.The magnitude of induced emf in the coil at the fourth second will be:

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A long solenoid of radius $R$ carries a time $\left(t\right)$dependent current $I\left(t\right)={I}_{0}t\left(1-t\right)$ . A ring of radius $2R$ is placed coaxially near its middle. During the time interval $0\le t\le 1,$ the induced current $\left({I}_{R}\right)$ and the induced $EMF\left({V}_{R}\right)$ in the ring change as:

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A conducting circular loop is placed in a uniform magnetic field, $B=0.025\mathrm{T}$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $1\mathrm{mm}{\mathrm{s}}^{-1}$. The induced emf when the radius is $2\mathrm{cm}$, is

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

The magnetic flux through a circuit of resistance $R$ changes by an amount $\Delta \varnothing $ in time $\Delta t$, Then the total quantity of electric charge $Q$. which is passing during this time through any point of the circuit is given by_____

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A semicircular wire of radius $r$ rotates in uniform magnetic field $B$ about its diameter with angular velocity $\omega $. If the total resistance of the circuit is $R$, then the mean power generated per period of rotation is

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A conducting metal circular-wire-loop of radius $r$ is placed perpendicular to a magnetic field which varies with time as $B={B}_{0}{e}^{-\frac{t}{\tau}},$ where ${B}_{0}\mathrm{and}\tau $ are constants at time $t=0$. If the resistance of the loop is $R$, then the heat generated in the loop after a long time $\left(t\to \infty \right)$ is

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A coil of cross-sectional area $A$ having$n$ turns is placed in a uniform magnetic field $B$. When it is rotated with an angular velocity $\mathrm{\omega ,}$ the maximum e.m.f. induced in the coil will be:

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Production of Induced EMF

A conducting circular loop made of a thin wire has area $3.5\times {10}^{-2}{\mathrm{m}}^{2}$ and resistance $10\mathrm{\Omega}$ It is placed perpendicular to a time-dependent magnetic field $B\left(t\right)=\left(0.4\mathrm{T}\right)\mathrm{sin}\left(50\pi t\right)$. The field is uniform in space. Then the net charge flowing through the loop during $t=0\mathrm{s}$ and $t=10\mathrm{ms}$ is close to: