Class 12 Electromagnetic Induction CBSE Questions & Answers

A loop of wire enclosing an area A is placed in a region where the magnetic field is perpendicular to the plane of the loop. The magnitude of B varies in time according to the expression B = \({{\rm{B}}_{{\rm{max}}}}{{\rm{e}}^{ - {\rm{at}}}}\), where a is some constant. That is, at \({\rm{t }} = {\rm{ }}0\) the field is \({{\rm{B}}_{{\rm{max}}}}\) , and for \({\rm{t }} > {\rm{ }}0\) , the field decreases exponentially . Induced emf in the loop as a function of time is

A long solenoid of radius R has n turns of wire per unit length and carries a time-varying current that varies sinusoidally as \({\rm{cos}}\omega \) t, where \({{\rm{I}}_{{\rm{max}}}}\) is the maximum current and \(\omega \) is the angular frequency of the alternating current source . Magnitude of the induced electric field outside the solenoid, a distance \({\rm{r }} > {\rm{ R}}\) from its long central axis.

An ac generator consists of 8 turns of wire, each of area \({\rm{A }} = {\rm{ }}0.0{\rm{9}}0{\rm{ }}0{\rm{ m2}}\) , and the total resistance of the wire is \({\rm{12}}.0{\rm{ }}\Omega \). The loop rotates in a 0.500-T magnetic field at a constant frequency of 60.0 Hz. Maximum induced emf is

Assume that a motor in which the coils have a total resistance of \({\rm{1}}0{\rm{ }}\Omega \) is supplied by a voltage of 120 V. When the motor is running at its maximum speed, the back emf is 70 V. Current in the coils when the motor is turned on and when it has reached maximum speed are

The magnetic field between the Horizontal poles of an electromagnet is uniform at any time, but its magnitude is increasing at the rate of 0.020 T/s.The area of a horizontal conducting loop in the magnetic field is 120\({\rm{c}}{{\rm{m}}^{\rm{2}}}\), and the total circuit resistance, including the meter, is \({\rm{5 }}\Omega \). Induced emf and the induced current in the circuit are

The magnetic field between the Horizontal poles of an electromagnet in is uniform at any time, but its magnitude is increasing at the rate of 0.020 T/s.The area of a loop made of perfect insulating material is 120\({\rm{c}}{{\rm{m}}^{\rm{2}}}\).This loop is kept horizontally in the magnetic field. Induced emf and the induced current in the circuit are

A 500-loop circular wire coil with radius 4.00 cm is placed between the poles of a large electromagnet. The magnetic field is uniform and makes an angle of \({\rm{6}}0^\circ \) with the plane of the coil; it decreases at 0.200 T/s . Magnitude of induced emf is

If two coils of inductances \({{\rm{L}}_{\rm{1}}}\) and \({{\rm{L}}_{\rm{2}}}\) are linked such that their mutual inductance is M, then

A small coil of radius r is placed at the centre of a large coil of radius R, where \({\rm{M }} = {\rm{ L1}} \times {\rm{L2}}\) R >> r. The two coils are coplanar. The mutual induction of the coils is proportional to

A uniformly wound long solenoid of inductance L and ressistance R is broken into two equal parts, which are then joined in parallel. This combination is then joined to a cell of emf \(\varepsilon \). The time constant of the cicuit is

A uniformly wound long solenoid of inductance L and ressistance R is broken into two equal parts, which are then joined in parallel. This combination is then joined to a cell of emf ε.The steady state current in the circuit is

When a coil is joined to a cell,current grows with a time constant \(\tau \) The current will reach \({\rm{1}}0\% \) of it's steady-state value in time

When a coi is joined to a cell grows with a time constant \(\tau \) .The current will reach \({\rm{1}}0\% \) less tan it's steady-state value in time

At \({\rm{t}} = 0\),an inductor of zero resistance is joined to a cell of emf \(\varepsilon \) through a resistance. The current decreases with a time constant \(\tau \) The emf across the coil after time t is

A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm \({{\rm{s}}^{ - {\rm{1}}}}\) in a direction normal to the shorter side of the loop? For how long does the induced voltage last ?