Electro magnetic induction practice · Medium

A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then

Three identical ring move with the same speed on a horizontal surface in a uniform horizontal magnetic field normal to the planes of the rings. The first (A) slips without rolling, the second (B) rolls without slipping, and the third rolls with slipping

Two concentric circular coils have radius $R_1$ and $R_2$ such that $R_1 \ll R_2$. If a current is setup in the second coil then the mutual inductance of first coil with respect to second coil depends upon

An electric motor operates on a $50\,\,volt$ supply and a current of $12\,A$. If the efficiency of the motor is $\mathrm{30}\,\,\mathrm{\% }$, what is the resistance of the winding of the motor

A long horizontal metallic rod with length along the east-west direction is falling under gravity. The potential difference between its two ends will

A coil has 1000 turns and $500\,\,\mathrm{c}{\mathrm{m}^2}$ as its area. The plane of the coil is placed of $2 \times {10^{ - 5}}\,\,\mathrm{web/}{\mathrm{m}^2}.$ The coil is rotated through ${180^0}$ in 0.2 seconds. The average emf induced in the coil, in milli volts is

A circular conducting loop of radius 10 cm is placed perpendicular to a uniform magnetic field of 1 T. if the magnetic field is made zero in a time interval of 0.1 s the emf induced in the loop during this time is.

A conducting rod of length $l$ is moving in a transverse magnetic field of strength $B$ with velocity $v$. The resistance of the rod is $R$. the current in the rod is

A magnet is allowed to move vertically through a resistance coil held horizontally. The
acceleration of the magnet is

Consider two identical, coaxial circular loops carrying a current i each, circulating in the same direction. If the loops approach each other

If a magnet is plugged into a coil, then the magnitude of induced emf does not depend upon

The self inductance of a long solenoid cannot be increased by

The self-inductance $L$ of a solenoid of length $l$ and area of cross-section $A$, with a fixed number of turns $N$ increases as

A field of strength $5 \times {10^4}/\pi$ Amp turns / meter acts at right angle to the coil of 50 turns of area ${10^{ - 2}}\,{m^2}$. The coil is removed from the field in 0.1 second. Then the induced emf in the coil is

Energy is stored in the choke coils in the form of

A rectangular coil of wire has dimensions $0.2 \mathrm{~m} \times 0.1 \mathrm{~m}$. The coil has 2000 turns. The coil rotates in a magnetic field about an axis parallel to its length and perpendicular to the magnetic field of $0.02 \mathrm{~Wb} \mathrm{~m}^{-2}$. The speed of rotation of the coil is $4200 \mathrm{rpm}$. Calculate

(i) the maximum value of the induced emf in the coil

(ii) the instantaneous value of induced emf when the plane of the coil has rotated through an angle of $30^{\circ}$ from the initial position.

An induced emf has

In what form is the energy stored in an inductor or
A coil of inductance $L$ is carrying a steady current $i$. What is the nature of its stored energy

A metal rod of length $1 \mathrm{~m}$ is rotated about one of its ends in a plane right angles to a field of inductance $2.5 \times 10^{-3}$ $\mathrm{Wb} / \mathrm{m}^2$. If it makes 1800 revolutions/min. Calculate induced e.m.f. between its ends.

A conducting loop of area $5.0 \mathrm{~cm}^2$ is placed in a magnetic field which varies sinusoidally with time as $B=B_0 \sin \omega t$ where $B_0=0.20 \mathrm{~T}$ and $\omega=300 \mathrm{~s}^{-1}$. The normal to the coil makes an angle of $60^{\circ}$ with the field. Find

(a) the maximum emf induced in the coil,

(b) the emf induced at $\tau=(\pi / 900)\text{ s}$ and

(c) the emf induced at $t=(\pi / 600) \mathrm{s}$.

According to Lenz’s law of electromagnetic induction

Certain galvanometers have a fixed core made of non magnetic metallic material. The function of this metallic material is

Over a solenoid of $50 \mathrm{~cm}$ length and $2 \mathrm{~cm}$ radius and having 500 turns, is wound another wire of 50 turns near the centre. Calculate the (i) mutual inductance of the two coils (ii) induced emf in the second coil when the current in the primary changes from 0 to $5 \mathrm{~A}$ in $0.02 \mathrm{~s}$.

Assertion (A) : In parallel, current distributes in inverse ratio of inductance $i \propto \frac{1}{L}$

Reason (R) : In electrical circuits, an inductor can be treated as a resistor.

Pick out the false statement from the following

A very small circular loop of radius $a$ is initially (at $t=0$ ) co-planar and concentric with a much larger fixed circular loop of radius $b$. A constant current $I$ flows in the larger loop. The smaller loop is rotated with a constant angular speed $\omega$ about the common diameter. The emf induced in the smaller loop as a function of time $t$ is

In an A.C. generator, when the plane of the armature is perpendicular to the magnetic field

A magnet is brought near a coil in two ways i. rapidly, ii. slowly. The induced charge will be:

Two identical coaxial coils P and Q carrying equal amount of current in the same direction are brought nearer. the current in

An inductor of inductance $20 \mathrm{mH}$ is connected across the terminals of a capacitor of capacitance $2 \mu \mathrm{F}$ which is initially charged to a potential $10 \sqrt{2} \mathrm{~V}$. The charge on the capacitor, when the energy stored in the capacitor becomes equal to the energy stored in the inductor is