Electro magnetic induction practice · Mixed difficulty

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

Lenz’s law is statement of

In a dc motor, induced e.m.f. will be maximum

The dimensions of self inductance are

A wire of length $2.5 \mathrm{~km}$ and resistance $35 \Omega$ has fallen from a height of $10 \mathrm{~m}$ in earth's horizontal field of $2 \times 10^{-5} \mathrm{~T}.$ The current through the wire is

Energy associated with a moving charge is due to

Use of eddy currents is done in the following expect

We can reduce eddy currents in the core of the transformer

The inductance of a coil is $L = 10\,\,\mathrm{H}$ and resistance $R = 5\,\,\mathrm{\Omega }$. If applied voltage of battery is $\mathrm{10 V}$ and it switches off in $\mathrm{1 \,milli\,second}$, find induced emf of inductor

Assertion: Induced emf will always occur when ever there is change in magnetic flux.

Reason: Current always induces whenever there is change in magnetic flux.

The coupling coefficient of the perfectly coupled coil is:

Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increasing with time. The induced current in the inner loop then, is

The average power dissipated in a pure inductance is

Statement I: A flexible wire loop of irregular shape carrying current when placed in a uniform external magnetic field acquires circular shape.

Statement II: Any current carrying loop when placed in external magnetic field tries to acquires minimum energy and hence maximum magnetic flux and for a given perimeter circular shape is having greatest area.

A uniformly wound solenoidal coil of self inductance $1.8 \times {10^{ - 4}}$ H and resistance 6 Ω is broken up into two identical coils. These identical coils are then connected in parallel across a 12 V battery of negligible resistance. The time constant of the current in the circuit