Electro magnetic induction practice · Mixed difficulty

An air cored coil has a self-inductance of 0.1 H. A soft iron core of relative permeability 100 is 1/10 th. The value of self-inductance now becomes

The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was

A coil of '$\mathrm{n}$' turns and resistance '$\mathrm{R}$' $\Omega$ is connected in series with a resistance $\frac{\mathrm{R}}{2}$. The combination is moved for time '$\mathrm{t}$' second through magnetic flux $\phi_1$ to $\phi_2$. The induced current in the circuit is

Focault’s currents are produced in a material when it is

A copper rod is moved in a magnetic field. The charge developed across its ends will be proportional to ____

The energy stored in an inductor of self inductance $L$ henry carrying a current of $\mathrm{1 }\,\mathrm{A}$ is

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

Coefficient of coupling between two coils of self-inductances ${L_1}\,\,\mathrm{and}\,\,{L_2}$ is unity. It means

A cylindrical bar magnet is kept along the axis of a circular coil. The magnet is rotated about its axis such that north pole faces the coil. The induced current in the coil

A rectangular coil of 100 turns and cross-sectional area $5 \times 10^{-3} \mathrm{~m}^2$ is placed perpendicular to a magnetic filed of $0.2 \mathrm{~T}$. If the field drops to $0.05 \mathrm{~T}$ in $0.5$ seconds, the magnitude of emf induced in the coil is ___.

Armature current in dc motor will be maximum when

Magnetic flux linked with a stationary loop of resistance $4 \Omega$ varies with respect to time during the time period 2 second, as follows: $\phi=3 t(2-t)$. Find the amount of heat generated (in joules) during that time.

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.

A sheet is placed on a horizontal surface in front of a strong magnetic pole. A force is needed to:

A. hold the sheet there if it is magnetic.

B. hold the sheet there if it is non-magnetic.

C. move the sheet away from the pole with uniform velocity if it is conducting.

D. move the sheet away from the pole with uniform velocity if it is both, non-conducting and non-polar.

Choose the correct statement(s) from the options given below:

A coil and a bulb are connected in series with a dc source, a soft iron core is then inserted in the coil. Then

A wire of length 50 cm is moving parallel to itself with a speed of $1 \mathrm{~m} / \mathrm{s}$ in a perpendicular magnetic field of $2 \times 10^{-4}$ tesla. The emf developed across its two ends is:

Two identical circular loops of metal wire are lying on a table. Loop $A$ carries a current which increases with time. In response, the loop $B$

The horizontal component of earth’s magnetic field at a place is $4 \times {10^{ - 4}}T$ and dip is $45^\circ$. A metal rod of length 20 cm is placed in north south direction and is moved at constant speed of 5 cm/s towards East. What is e.m.f induced in the rod ?

A particle mass m, charge Q and kinetic
energy T enters a transverse uniform
magnetic field of induction B after 3s the
kinetic energy of the particle will be

A coil has an area of $0.05\,\,{m^2}$ and it has $\mathrm{800}$ turns. It is placed perpendicularly in a magnetic field of strength $4 \times {10^{ - 5}}\,\,Wb/{m^2}$, it is rotated through $90^\circ$ in $0.1\,\sec$. The average e.m.f. induced in the coil is

The net magnetic flux through any closed surface, kept in a magnetic field is

Induction furnace uses ……… to produce heat.

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

Statement (A): The alternating current lags behind the e.m.f. by a phase angle of $\frac{\pi }{2},$ when ac flows through an inductor.
Statement (B): A bulb connected in series with a solenoid is connected to ac source. If a soft iron core is introduced in the solenoid, the bulb will glow brighter.
Statement (C): The dc and ac both can be measured by a hot wire instrument.

Two coils A and B have coefficient of mutual inductance M = 2H. The magnetic flux passing through coil A changes by 4 Wb in 10 s due to change in current in B. Then

Pick out the false statement from the following

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

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

For a coil having L = 2 mH, current flows at the rate of ${10^3}\;\mathrm{A}{\mathrm{s}^{ - 1}}$. The emf induced is

If a copper ring is moved quickly towards south pole of a powerful stationary bar magnet, then