Electro magnetic induction practice · Medium

Changing magnetic fields can set up current loops
in nearby metal bodies and the currents are called
as

If $\mathrm{N}$ is the number of turns in a coil, the value of self inductance varies as

Magnetic flux linked with a coil is $\phi = 5\,{t^2} + 2\,t + 3$, where $t$ is second and $\phi$ is in weber. At time $t = 1\mathrm{ }s$, the value of induced emf in volt

A $12 \, \mathrm{V}$ battery connected to a coil of resistance $6 \, \Omega$ through a switch, drives a constant current in the circuit. The switch is opened in $1 \, \mathrm{ms}$. The emf induced across the coil is $20 \, \mathrm{V}$. The inductance of the coil is :

Two inductances each of inductance ‘L’ are joined in parallel their equivalent inductance is

A train is running at a speed of $72 \mathrm{~km} \mathrm{~hr}^{-1}$ on the rails separated by a distance of $150 \mathrm{~cm}$. If the vertical component of earth's magnetic field at the place is $4.0 \times 10^{-5} \mathrm{~T}$. The induced emf on the rails is

The momentum in mechanics is expressed as $m\,\, \times \,\,V$. The analogous expression in electricity is

A 10-meter wire is kept in east-west direction. It is falling down with a speed of $5.0 \mathrm{~meter} / \mathrm{second}$, perpendicular to the horizontal component of earth's magnetic field of $0.30 \times 10^{-4}$ weber $/$ meter $^2$. The momentary potential difference induced between the ends of the wire will be

An inductor coil stores $32 \mathrm{~J}$ of magnetic field energy and dissipates energy as heat at the rate $320 \mathrm{~W}$ when a current of $4 \mathrm{~A}$ is passed through it. The time constant of the circuit when this coil is joined across an ideal battery will be

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

The mutual inductance between two coils is $0.09$ Henry. If the current in the primary coil changes from 0 to $20 \mathrm{~A}$ in $0.006 \mathrm{~s}$, the e.m.f. induced in the secondary coil at that instant is

Two identical circular coils A and B are kept on a horizontal tube side by side without touching each other. If the current in the coil A increases with time, in response, the coil B :

The currents in two coils of self- inductance $5 \mathrm{~mH}$ and $1 \mathrm{~mH}$ are increasing at the same rate at a certain instant. The power supplied to the coils is also same. Then identify the false statement among the following

A solenoidal coil has 50 turns per $\mathrm{cm}$ along its length and a cross-sectional area of $4 \times 10^{-4} \mathrm{~m}^2 .200$ turns of another wire is wound round the first solenoid co-axially. Both the two coils are electrically insulated from each other. Calculate the mutual inductance between the two coils.

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

Assertion : A small magnet takes longer time in falling in a hollow metallic tube without touching the wall.

Reason : There is opposition of motion due to production of eddy currents in metallic tube.

Lenz's law provides a relation between

A short solenoid of radius $a$, number of turns per Unit length $n_1$ and length $L$ is kept coaxially inside a very long solenoid of radius $b$, the number of turns per Unit length $n_2$. What is the mutual inductance of the system?

In $\mathrm{0}\mathrm{.1 s}$, the current in a coil increases from $\mathrm{1}\,\mathrm{A}$ to $\mathrm{1.5}\,\mathrm{A}$. If inductance of coil is $\mathrm{60}\,\,\mathrm{mH}$, then induced current in external resistance of $3\,\mathrm{\Omega }$ will be

Two inductors $\mathrm{A}$ and $\mathrm{B}$ when connected in parallel are equivalent to a single inductor of inductance $1.5 \mathrm{~H}$, and when connected in series are equivalent to a single inductor of inductance $8 \mathrm{~H}$. Find the difference in the inductances of $\mathrm{A}$ and $\mathrm{B}$.

Self induction of a solenoid is

If a bar magnet is dropping through the copper ring, then its velocity

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

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