Electro magnetic induction practice · Medium

The magnetic flux linked with a coil of N turns of area of cross section A held with its plane parallel to the field B is

The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following conditions is correct

The total charge, induced in a conducting loop, when it is moved in a magnetic field depends on

When a bar magnet falls through a long hollow metal cylinder fixed with its axis vertical, the final acceleration of the magnet is

Self inductance of primary and secondary of a perfectly coupled coils are $4 \mathrm{~mH}$ and $9 \mathrm{~mH}$ respectively. The coefficient of mutual inductance between them is

The direction of magnetic lines of force produced by passing a direct current in a conductor is given by

Two concentric circular coils, one of small radius $\mathrm{r}$ and the other of large radius $\mathrm{R}$ are placed co-axially with centers coinciding. If the radius $\mathrm{r}$ is changed by $2 \%$, then the change in mutual inductance of the arrangement is (Assume, $\mathrm{r} << \mathrm{R}$)

Assertion: Induced electric field lines form closed loops in space.

Reason : Induced electric field lines do not originate & terminate at charged particle.

Which of the following is constructed on the principle of electromagnetic induction

A solenoid of radius $4 \mathrm{~cm}$ and 1000 turns, carries a current of $8 \mathrm{~A}$. If it is equivalent to a magnet of same size and magnetization $\vec{M}$ (Magnetic moment/Volume) of $2000 \, \mathrm{Am}^{-1}$, then the length of the solenoid is

A conducting rod of length $\mathrm{L}$ is moving in a uniform magnetic field $(\mathrm{B})$ with a velocity $\mathrm{v}$ without rotation. The velocity of the rod is perpendicular to the rod, and the motion of the rod is confined to a plane perpendicular to the magnetic field. What is the induced emf developed across the rod?

A wheel with ten metallic spokes each 0.5 m long is rotated with a speed of 120 rev/min in a plane normal to the earths magnetic field at the place. If the magnitude of the field is 0.4 gauss, the induced e.m.f between the axle and the rim of the wheel is equal to

A primary coil and secondary coil are placed close to each other. A current, which changes at the rate of $25 \mathrm{~A}$ in a millisecond, is present in the primary coil. If the mutual inductance is ${92}\times 10^{-6} \mathrm{~H}$, then the value of induced emf in the secondary coil is

A small coil of radius $r$ is placed at the centre of a large coil of radius $R$, where $R > > r$. The two coils are coplanar. The mutual induction between the coils is proportional to

Which of the following phenomena is utilised in the construction of mouth piece of a telephone now a days?

Two identical induction coils each of inductance $L$ joined in series are placed very close to each other such that the winding direction of one is exactly opposite to that of the other, what is the net inductance?

The approximate formula expressing the formula of mutual inductance of two thin coaxial loops of the same radius $a$ when their centers are separated by a distance $l$ with $l \gg a$ is

The mutual inductance of a pair of coils is $0.75\,\mathrm{H}$. If current in the primary coil changes from $0.5 \mathrm{~A}$ to zero in $0.01 \mathrm{~s}$ find average induced e.m.f. in secondary coil.

A wire loop that encloses an area of $20 \mathrm{~cm}^2$ has a resistance of $10 \Omega$. The loop is placed in a magnetic field of $2.4 T$ with its plane perpendicular to the field. The loop is suddenly removed from the field. How much charge flows pass a given point in the wire?

Two coil $\mathrm{A}$ and $\mathrm{B}$ have mutual inductance $2 \times 10^{-2}$ henry. If the current in the primary is $\mathrm{I}=5 \sin (10 \pi \mathrm{t})$ then the maximum value of e.m.f. induced in coil $\mathrm{B}$ is

The phenomenon called electromagnetic induction was first investigated by

Assertion(A): $L/R$ and $CR$ both have same dimensions.

Reason(R): ${L}/{R}$ and ${CR}$ are time constants.

Assertion: Magnetic flux is a vector qunatity

Reason: Value of magnetic flux can be positive, negative or zero.

Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon

I. relative position and orientation of the two coils

II. the materials of the wires of the coils

III. the rates at which currents are changing in the two coils

Which of the above statements is/are correct?

A 10 m long horizontal wire extends from North-East to South-West. It is falling with a speed of $5.0\,\,\,m{s^{ - 1}}$ at right angles to the horizontal component of the earth’s magnetic field of $0.3 \times {10^{ - 4}}\,Wb/{m^2}.$ The value of the induced emf in wire is

A closed surface $S$ encloses a magnet of magnetic moment $2 \mathrm{~ml}$. The magnetic flux emerging from the surface is

A magnet is dropped down an infinitely long vertical copper tube

Assertion (A): Electromagnetic force is enormously strong as compared to gravitational force. Yet, gravity dominates in the large-scale phenomena (e.g. formation of galaxies).
Reason (R): Existence of positive and negative charges make matter mostly electrically neutral.
Which of the following is true?

A gold rod of length $l$ is accelerated in the horizontal direction with an acceleration $a_0$. The rod is held between two perfectly insulating clamps. Calculate the electric field set up in the rod. Take the mass of electron as $m$.

The magnetic potential energy stored in a certain induction is $\mathrm{25}{\mkern 1mu} {\mkern 1mu} \,mJ$, when the current in the inductors is $\mathrm{60}{\mkern 1mu} {\mkern 1mu} mA$. This inductors is of inductance