Electro magnetic induction practice · Mixed difficulty

In a coil, the current changes form $-2 \mathrm{~A}$ to $+2 \mathrm{~A}$ in $0.2 \mathrm{~s}$ and induces an emf of $0.1 \mathrm{~V}$. The selfinductance of the coil is :

An iron is placed parallel to the magnetic field of intensity $2000 \frac{\mathrm{A}}{\mathrm{m}}$. The magnetic flux through the rod is $6 \times 10^{-4} \mathrm{~Wb}$ and its cross-sectional area is $3 \mathrm{~cm}^2$. The magnetic permeability of the rod in $\frac{\mathrm{W b}}{\mathrm{A-m}}$ is

The net magnetic flux through any closed surface is

The magnetic flux linked with the coil varies with time as $\phi = 3\,{t^2} + 4\,t + 9$. the magnitude of the induced emf at $\mathrm{2}\,\mathrm{s}$ is

When current $\mathrm{i}$ passes through an inductor of self inductance $\mathrm{L}$, energy stored in it is $1 / 2 . \mathrm{Li}^2$. This is stored in the

A ring of radius a rotates with a constant angular velocity $\omega$ about its axis (passing through its centre and perpendicular to its plane). The ring is in $x-y$ plane. The potential difference induced in the ring would be zero, if uniform magnetic field is along

A rectangular loop of sides $\mathrm{10}\,\mathrm{cm}$ and $\mathrm{5}\,\mathrm{cm}$ with a cut is stationary between the pole pieces of an electromagnet. The magnetic field of the magnet is normal to the loop. The current feeding the electromagnet is reduced so that the field decreased from its initial value of $\mathrm{0}\mathrm{.3 T}$ at the rate of $0.02\,\,\mathrm{\Omega }$. If the cut is joined and the loop has a resistance of $2.0\,\,\mathrm{\Omega }$, the power dissipated by the loop as heat is

An ideal capacitor of capacitance $0.2\mu F$ is charged to a potential difference 10V. The charging battery is then disconnected. The capacitor is then connected to an ideal number of self inductance 0.5mH. The current at a time when the potential difference across the capacitor is 5V, is

A coil of self- inductance $L$ is connected in series with a bulb $B$ and an AC source. Brightness of the bulb decreases when

I) number of turns inthe coil is reduced

II) a capacitance of reactance $X_C=X_L$ is included in the same circuit

III) an iron rod is inserted in the coil which of the above statements is /are correct?

Two similar circular loops carry equal currents in the same direction. On moving coils further apart, the electric current will

Assertion(A): An inductor in a D.C. circuit opposes both a steady current and a changing current.

Reason(R): Induced emf is generated only when the flux linked with the inductor remains unchanged.

Assertion (A): Only a change in magnetic flux will maintain an induced current in a closed coil.

Reason (R): The presence of large magnetic flux through a coil maintains a current in the coil if the coil is continuous.

The relation between the charge flow $\Delta \mathrm{Q}$ through the circuit of resistance $\mathrm{r}$ and the change in the magnetic flux $\Delta \phi_{\mathrm{B}}$ is

The working of a dynamo is based on the principle of

The magnitude of induced emf is directly proportional to the rate of change of magnetic flux linked with the coil. This statement is known as

ISRO observed the wavelength of sodium line emitted by a star is 589.6 nm. The actual wavelength emitted by star is 589 nm. The speed of the star with respect to us would be

Energy is stored in the choke coils in the form of

The magnetic flux linked with a loop is $\phi=6 \mathrm{t^2+7 t+1}$ where $\phi$ is in milli weber and $\mathrm{t}$ is in second. What will be the e.m.f. induced at $\mathrm{t}=2 \mathrm{~sec}$?

A small piece of metal wire is dragged across the gap between the pole pieces of a magnet in $\mathrm{0}.\mathrm{5}\,\,\mathrm{second}$. The magnetic flux between the pole pieces is known to be $8 \times {10^{ - 4}}\,\,Wb$. The emf induced in the wire is

The current in an ideal, long solenoid is varied at a uniform rate of $0.01 \mathrm{~As}^{-1}$. The solenoid has 2000 turns/m and its radius is $6.0 \mathrm{~cm}$.

(a) Consider a circle of radius $1.0 \mathrm{~cm}$ inside the solenoid with its axis coinciding with the axis of the solenoid. Write the change in the magnetic flux through this circle in 2.0 seconds.

(b) Find the electric field induced at a point on the circumference of the circle.

(c) Find the electric field induced at a point outside the solenoid at a distance $8.0 \mathrm{~cm}$ from its axis.

Mutual inductance of two coils can be increased by

Assertion: The induced emf and current will be same in two identical loops of copper and aluminium, when rotated with same speed in the same magnetic field.

Reason: Mutual induction does not depend on the orientation of the coils.

There is a uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then

According to phenomenon of mutual inductance

Faraday's law among the following is ____

A circular loop of radius $\frac{10}{\sqrt{\pi}} {cm}$ is placed in a uniform time varying magnetic field with field being perpendicular to the plane of the loop. If the field decreases from $0.5 {~T}$ to zero in $0.5\, {sec}$, then induced emf in the loop at $0.25 \,{sec}$. is :

The direction of magnetic field $\mathrm{dB}$ due to current element $d I$ at a distance $r$ is the direction of

Principle of working of AC generator is

What is the self inductance of an air core solenoid 1 m long, diameter 0.05m, if it has 500 turns? Take ${\pi ^2} = 10.$

Average energy stored in a pure inductance $L$ when a current $i$ flows through it, is