Electromagnetic Induction

Two solenoids of equal number of turns have their lengths as well as radii in the same ratio $1: 3$. The ratio of their self inductance will be

When the number of turns in a coil are made 3 times without any change in the length of the coil, its self inductance becomes

A metal disc of radius R rotates with an angular velocity $\omega$ about an axis perpendicular to its plane passing through its centre in a magnetic field of induction B acting perpendicular to the plane of the disc. The induced e.m.f. betw...

An air cored coil has a self inductance 0.1 H . A soft iron core of relative permeability 1000 is introduced and the number of turns is reduced $\left(\frac{1}{10}\right)^{\text {th }}$. The value of self inductance is

The coefficient of mutual induction is 2 H and induced e.m.f. across secondary is 2 kV Current in the primary is reduced from 6 A to 3 A . The time required for the change of current is

When the number of turns in a coil is doubled without any change in the length of the coil, its self-inductance

A closely wound coil of 100 turns and of crosssection $1 \mathrm{~cm}^2$ has coefficient of self inductance 1 mH . The magnetic induction at the centre of the core of a coil when a current of 2 A flows in it, will be (in $\mathrm{Wb} / \mat...

The number of turns in the primary of a transformer are 1000 and in secondary 3000. If 80 V a.c. is applied to the primary, the potential difference per turn of the secondary coil is

If number of turns per unit length in a solenoid is tripled, the self inductance of solenoid will

Two coils have a mutual inductance 0.003 H . The current changes in the first coil according to equation $I=I_0 \sin \omega t$, where $I_0=8 \mathrm{~A}$ and $\omega=100 \pi \mathrm{rad} \mathrm{s}^{-1}$. The maximum value of e.m.f. in the ...

The current in LR circuit if reduced to half What will be the energy stored in it?

An inductor coil of inductance $L$ is divided into two parts and both parts are connected in parallel. The net inductance is

If current of 4 A produces magnetic flux of $3 \times 10^{-3} \mathrm{~Wb}$ through a coil of 400 turns, the energy stored in the coil will be

Two concentric circular coils having radii ' $r_1{ }^{\prime}$ and ' $r_2$ ' $\left(r_2 \ll r_1\right)$ are placed co-axially with centres coinciding. The mutual inductance of the arrangement is ( $\mu_0=$ permeability of free space) (Both ...

Self inductance of solenoid is

A conducting wire of length \(2500 \mathrm{~m}\) is kept in east-west direction, at a height of \(10 \mathrm{~m}\) from the ground. If it falls freely on the ground then the current induced in the wire is (Resistance of wire $$=25 \sqrt{2} ...

An electron (mass \(\mathrm{m}\) ) is accelerated through a potential difference of '\(V\)' and then it enters in a magnetic field of induction '\(B\)' normal to the lines. The radius of the circular path is (\(\mathrm{e}=\) electronic char...

The magnetic flux through a loop of resistance \(10 ~\Omega\) varying according to the relation \(\phi=6 \mathrm{t}^2+7 \mathrm{t}+1\), where \(\phi\) is in milliweber, time is in second at time \(\mathrm{t}=1 \mathrm{~s}\) the induced e.m....

The mutual inductance (M) of the two coils is \(3 ~\mathrm{H}\). The self inductances of the coils are \(4 ~\mathrm{H}\) and \(9 ~\mathrm{H}\) respectively. The coefficient of coupling between the coils is

Two coils \(\mathrm{A}\) and \(\mathrm{B}\) have mutual inductance 0.008 \(\mathrm{H}\). The current changes in the coil A, according to the equation \(\mathrm{I}=\mathrm{I}_{\mathrm{m}} \sin \omega \mathrm{t}\), where $$\mathrm{I}_{\mathrm...

If current '\(I\)' is flowing in the closed circuit with collective resistance '\(R\)', the rate of production of heat energy in the loop as we pull it along with a constant speed '\(\mathrm{V}\)' is ( \(\mathrm{L}=\) length of conductor, $...

The alternating e.m.f. induced in the secondary coil of a transformer is mainly due to

A magnetic field of \(2 \times 10^{-2} \mathrm{~T}\) acts at right angles to a coil of area \(100 \mathrm{~cm}^2\) with 50 turns. The average e.m.f. induced in the coil is \(0.1 \mathrm{~V}\), when it is removed from the field in time '$$t$...

The self induction (L) produced by solenoid of length '\(l\)' having '\(\mathrm{N}\)' number of turns and cross sectional area '\(A\)' is given by the formula (\(\phi=\) magnetic flux, \(\mu_0=\) permeability of vacuum)

A coil having effective area A, is held with its plane normal to magnetic field of induction B. The magnetic induction is quickly reduced by \(25 \%\) of its initial value in 2 second. Then the e.m.f. induced across the coil will be

A long solenoid has 1500 turns. When a current of \(3.5 \mathrm{~A}\) flows through it, the magnetic flux linked with each turn of solenoid is \(2.8 \times 10^{-3}\) weber. The self-inductance of solenoid is

A transformer has 20 turns in the primary and 100 turns in the secondary coil. An ac voltage of \(\mathrm{V}_{\text {in }}=600 \sin 314 \mathrm{t}\) is applied to primary terminal of transformer. Then maximum value of secondary output volta...

The magnet is moved towards the coil with speed '\(\mathrm{V}\)'. The induced e.m.f. in the coil is '\(\mathrm{e}\)'. The magnet and the coil move away from one another each moving with speed '\(\mathrm{V}\)'. The induced e.m.f. in the coil...

Three coils of inductance \(\mathrm{L}_1=2 \mathrm{H}, \mathrm{L}_2=3 \mathrm{H}\) and \(\mathrm{L}_3=6 \mathrm{H}\) are connected such that they are separated from each other. To obtain the effective inductance of 1 henry, out of the follo...

A conductor \(10 \mathrm{~cm}\) long is moves with a speed \(1 \mathrm{~m} / \mathrm{s}\) perpendicular to a field of strength \(1000 \mathrm{~A} / \mathrm{m}\). The emf induced in the conductor is (Given : $$\mu_0=4 \pi \times 10^{-7} \mat...

A metal disc of radius \(R\) rotates with an angular velocity \(\omega\) about an axis perpendicular to its plane passing through its centre in a magnetic field of induction \(B\) acting perpendicular to the plane of the disc. The magnitude...

Two coils have a mutual inductance of \(0.004 \mathrm{~H}\). The current changes in the first coil according to equation \(\mathrm{I}=\mathrm{I}_0 \sin \omega \mathrm{t}\), where \(\mathrm{I}_0=10 \mathrm{~A}\) and $$\omega=50 ~\pi \mathrm{...

Two inductors of \(60 \mathrm{~mH}\) each are joined in parallel. The current passing through this combination is \(2.2 \mathrm{~A}\). The energy stored in this combination of inductors in joule is

Inductance per unit length near the middle of a long solenoid is \(\left(\mu_0=\right.\) permeability of free space, \(\mathrm{n}=\) number of turns per unit length, \(\mathrm{d}=\) the diameter of the solenoid)

An air craft of wing span \(40 \mathrm{~m}\) files horizontally in earth's magnetic field \(5 \times 10^{-5} \mathrm{~T}\) at a speed of \(500 \mathrm{~m} / \mathrm{s}\). The e.m.f. generated between the tips of the wings of the air craft i...

SI units of self inductance is

To manufacture a solenoid of length \(1 \mathrm{~m}\) and inductance \(1 \mathrm{~mH}\), the length of thin wire required is
(cross - sectional diameter of a solenoid is considerably less than the length)

The mutual inductance of a pair of coils, each of '\(N\)' turns, is '\(M\)' henry. If a current of '\(I\)' ampere in one of the coils is brought to zero in '\(t\)' second, the e. m. f. induced per turn in the other coil in volt is

When a current of \(1 \mathrm{~A}\) is passed through a coil of 100 turns, the flux associated with it is \(2.5 \times 10^{-5} \mathrm{~Wb} /\) turn. The self inductance of the coil in millihenry is

A coil of radius '\(r\)' is placed on another coil (whose radius is \(\mathrm{R}\) and current flowing through it is changing) so that their centres coincide \((\mathrm{R} \gg \mathrm{r})\). If both the coils are coplanar then the mutual in...

A coil having effective area '\(A\)' is held with its plane normal to a magnitude field of induction '\(\mathrm{B}\)'. The magnetic induction is quickly reduced to \(25 \%\) of its initial value in 1 second. The e.m.f. induced in the coil (...

The self inductance '\(L\)' of a solenoid of length '\(l\)' and area of cross-section '\(\mathrm{A}\)', with a fixed number of turns '\(\mathrm{N}\)' increases as

The magnetic flux through a circuit of resistance '\(R\)' changes by an amount \(\Delta \phi\) in the time \(\Delta t\). The total quantity of electric charge '\(Q\)' which passes during this time through any point of the circuit is

Two conducting circular loops of radii '\(R_1\)' and '\(R_2\)' are placed in the same plane with their centres coinciding. If \(R_1>R_2\), the mutual inductance \(M\) between them will be directly proportional to

A square loop of area \(25 \mathrm{~cm}^2\) has a resistance of \(10 \Omega\). This loop is placed in a uniform magnetic field of magnitude \(40 \mathrm{~T}\). The plane of loop is perpendicular to the magnetic field. The work done in pulli...

A graph of magnetic flux \((\phi)\) versus current (I) is plotted for four inductors A, B, C, D. Larger value of self inductance is for inductor

Two concentric circular coils having radii \(r_1\) and \(r_2\left(r_2 << r_1\right)\) are placed co-axially with centres coinciding. The mutual induction of the arrangement is (Both coils have single turn, \(\mu_0=\) permeability of free sp...

A hollow metal pipe is held vertically and bar magnet is dropped through it with its length along the axis of the pipe. The acceleration of the falling magnet is ( \(\mathrm{g}=\) acceleration due to gravity)

A graph of magnetic flux \((\phi)\) versus current (I) is drawn for four inductors A, B, C, D. Larger value of self inductance is for inductor.

Self inductance of a solenoid cannot be increased by