Electro magnetic induction practice · Medium

The working of a dynamo is based on the principle of

A uniform magnetic field $B$ exists in a direction perpendicular to the plane of a square loop made of a metal wire. The wire has a diameter of 4 mm and a total length of 30 cm. The magnetic field changes with time at a steady rate $\mathrm{d}B/dt = \mathrm{0}\mathrm{.032 \,\,T}{\mathrm{s}^{ - 1}}\mathrm{.}$ The induced current in the loop is close to (Take, resistivity of the metal wire $= 1.\mathrm{23} \times \mathrm{1}{\mathrm{0}^{ - 8}}\Omega \mathrm{m)}$

Two parallel rails of a railway track insulated from each other and with the ground are connected to a millivoltmeter. The distance between the rails is one metre. A train is travelling with a velocity of $72\,\,km{\mathrm{h}^{ - 1}}$ along the track. The reading of the millivotmeter (in $\mathrm{mV}$) is : (Vertical component of the earth’s magnetic induction is $2\,\, \times {10^{ - 5}}\,\mathrm{T})$

If a coil of metal wire is kept stationary in a non-uniform magnetic field, then

A conductor of length $l$ is kept in a magnetic field of strength $\mathrm{B}$. A current $\mathrm{I}$ passes through the conductor. The force experienced by the conductor is proportional to

Assertion: Faraday's copper disc generator is based on dynamic electromagnetic induction.

Reason: Alternating current generator is based on periodic electromagnetic induction.

A horizontal straight conductor when placed along south-north direction falls under gravity; there is

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

Assertion (A) : If some ferromagnetic substance is filled inside a solenoid, its coefficient of self induction $L$ will increase.

Reason (R) : By increasing the current in a coil, its coefficient of self induction $L$ can be increased.

Assertion : An emf is induced in long solenoid by a small bar magnet that moves while totally inside it along the solenoid axis.

Reason : As the magnet moves inside the solenoid, the flux through individual turns of the solenoid does not change.

Magnetic flux is

A wire of length $\mathrm{50}\,\,\mathrm{cm}$ moves with a velocity of $\mathrm{300}\,\,\mathrm{m - mi}{\mathrm{n}^{\mathrm{ - 1}}}$, perpendicular to a magnetic field. If the emf induced in the wire is $\mathrm{2}\,\mathrm{V}$, the magnitude of the field in telsa is

Choke coil works on the principle of

A short magnet is allowed to fall from rest along the axis of a horizontal conducting ring. The distance fallen by the magnet in one second may be

A thin circular ring of area $\mathrm{A}$ is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is $\mathrm{R}$. When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is

The number of turns of primary and secondary coils of a transformer are $\mathrm{5}\,\,\mathrm{and}\,\mathrm{10}$ respectively and the mutual inductance of the transformer is $25\,\,henry$. Now the number of turns in the primary and secondary of the transformer are made $\mathrm{10}\,\,\mathrm{and}\,\mathrm{5}$ respectively. The mutual inductance of the transformer in $henry$ will be

The mutual inductance between two coils is $2.5 \mathrm{~H}.$ If the current in one coil is changed at the rate of $1 \mathrm{~As}^{-1},$ what will be the emf induced in the other coil?

The mutual inductance between two coils depends upon

Assertion: At any instant, if the current through an inductor is zero, then the induced emf may not be zero

Reason: An inductor tends to keep the flux (i.e. current) constant

An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of

Assertion : The quantity L/R possesses dimension of time.

Reason : To reduce the rate of growth of current through a solenoid, we should increase the time constant (L/R).

Current in a coil falls from 5.0 A to 1.0 A in 0.1 s. If an average emf of 200 V is induced, then self-inductance of the coil is

The magnetic flux linked with a coil is $\phi$ and the emf induced in it is $\mathrm{e}$

The emf induced in the secondary coil due to unit rate of change of current in the primary is called _______

If rotational velocity of a dynamo armature is doubled, then induced e.m.f. will become

A circular ring of diameter $\mathrm{20}\,\mathrm{cm}$ has a resistance of $0.01\,\,\mathrm{\Omega }$. The charge that will flow through the ring if it is turned from a position perpendicular to a uniform magnetic field of $\mathrm{2}.\mathrm{0}\,\mathrm{T}$ to a position to the field is about

A capacitor (without dielectric) is discharging through a resistor. At some instant a dielectric is inserted between the plates, then

$5\,\,cm$ long solenoid having $10\,\,ohm$ resistance and $5\,\,mH$ inductance is joined to a $10\,\,volt$ battery. At steady state the current through the solenoid in ampere will be

The current in a coil changes from 0 to $2 \mathrm{~A}$ in $0.05 \mathrm{~s}$. If the induced emf is $80 \mathrm{~V}$, the self-inductance of the coil is,

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.