Electro magnetic induction practice · Mixed difficulty

A coil of cross-sectional area A having n turns is placed in a uniform magnetic field B. When it is rotated with an angular velocity $\omega$, the maximum e.m.f. induced in the coil will be

A wire of given length is bent in the form of a ring of diameter 2 a having self inductance $(L)$, then $L$ will depend upon following

The expression for the induced emf contains negative sign $\left(\mathrm{E}=\frac{-\mathrm{d} \phi}{\text {dt}}\right)$. What is the significance of negative sign?

A loop of area $1 \mathrm{~m}^2$ is placed in a magnetic field $B=2 \mathrm{~T}$, such that plane of the loop is parallel to the magnetic field. If the loop is rotated by $180^{\circ}$, the amount of net charge passing through any point of loop, if its resistance is $10 \Omega$, is

A planar loop of wire rotates in a uniform magnetic field. Initially at $t = 0$, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of 10 s about an axis in its plane, then the magnitude of induced emf will be maximum and minimum respectively at

The inductance $\mathrm{L}$ of a solenoid depends upon its radius $\mathrm{R}$ as

In an inductor, the current $\mathrm{I}$ varies with time t as $\mathrm{I=4+4 t}$. If the emf induced in the inductor is $8 \mathrm{~mV}$, what is self inductance? (Here current is in ampere and time is in second)

$Weber/{m^2}$ is equal to

If the magnetic flux through a coil at any time $\mathrm{t}$ is given by $\phi=\left(4 \mathrm{t^2+5 t}-3\right)$, then the increase in induced emf (in volt) 2 second after $\mathrm{t}=0$ is

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

Eddy current are produced when

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.

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

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

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

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

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

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

Current in a coil changes from $\mathrm{5}\,\,\mathrm{A}$ to $\mathrm{10}\,\,\mathrm{A}$ in $\mathrm{0}.\mathrm{2}\,\,\mathrm{s}$. If the coefficient of self-induction is $\mathrm{10}\,\,\mathrm{H}$, then the induced emf is

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?