A square loop of sides 4 cm having a resistance of 2$\Omega$ is placed normal to a magnetic field. If the magnetic field is gradually reduced at the rate of 0.02 T/s. The induced current in the loop is

The direction of the runway on the airport should be

A metallic wheel (of radius l and 8 spokes) is rotated in a uniform magnetic field B as shown. The motional EMF across centre and rim is given by

Charged pollen grains are lying on a frictionless table. These are now subject to a certain field and are found to be moving by these fields. The field cannot be

The magnetic field in the region is decreasing in such a way that dB/dt = $\gamma$. If resistance per unit length of the loop shown is $\lambda$, then, the current flowing in the loop is given by

A rectangular coil of wire rotates about an axis which is perpendicular to a uniform magnetic field at a steady rate. Consider the instant when the plane of the coil is parallel to the magnetic field lines. At that instant the induced electromotive force is :

There is a solenoid of length 1.5 m having 1000 turns per metre, kept in a region where the magnetic field is increased with time as 0.2 T s^-1. (radius of the solenoid is $\frac{10}{\sqrt{\mathrm{\pi }}}\mathrm{cm}$). The current through resistance 10$\Omega$ is

A one-metre long metallic rod is rotated with an angular frequency of 400 radians/sec about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant uniform magnetic field of 0.5 tesla parallel to the axis exists everywhere. The emf developed between the centre and the ring is

Self-inductances of primary and secondary of an ideal transformer are 90 mH and 40 mH. If the current in the primary decreases at the rate 10³ As^-1, then emf across the secondary is

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

In the figure as shown, straight wire carries a constant current. The direction of induced current in the rotating loop about an axis xx' at the instant shown

The figure shows a circular region of radius R in which uniform magnetic field is increasing at a constant rate dB/dt = $\alpha$. The induced electric field at a distance r from the centre is

If the instantaneous charge in the capacitor is 400$\mu$C and current through the circuit is decreasing at the rate 10³ A/s, then potential difference V_A-V_B is equal to

A uniform rod rotates in a uniform magnetic field B (perpendicular to its length) about its one of the end with constant angular velocity. The electric field produced is

When the current in a coil changes from 0 to 5 A, in 0.5 s, the average induced emf in the coil is 1 volt. The self-inductance of the coil is

The magnetic flux linked with a coil varies with time as $\varphi = 2t^2-6t+5$, where $\varphi$ is in weber and t is in second. The induced current is zero at

Choke coil works on the principle of

Assertion: Self-inductance is called the inertia of electricity.

Reason: It is on account of self-inductance that the coil opposes any change in current passing through it. 

Assertion: When a piece of non-metal and a metal are dropped from the same height near the surface of the earth the non-metallic piece will reach the ground first.

Reason: Induced current in metal will decrease the acceleration.

Assertion: Iron loss is minimized by using a laminated core.

Reason: Lamination of core restricts eddy current.

Assertion: The induced electric field is non-conservative.

Reason: Work done in a closed path in the induced electric field is nonzero.

Assertion: Lenz's law is in accordance with the conservation of energy.

Reason: The amount of mechanical energy lost against the induced emf or current is equal to the electrical energy reappearing in the circuit.

Assertion: Time-dependent magnetic field generates an electric field.

Reason: Direction of the electric field generated from the time-variable magnetic field does not obey Lenz's law.

Assertion: If the current passing through an inductor varies with time (t) as $t^2$, the induced emf will vary as a straight line.

Reason: EMF through an inductor is given by $\mathrm{E}=-\mathrm{L}\frac{\mathrm{dl}}{\mathrm{dt}}$.

Assertion: Group of inductors behave in the same way as a group of capacitors.

Reason: ${\mathrm{L}}_{\mathrm{series}}=\frac{{\mathrm{L}}_1+{\mathrm{L}}_2+{\mathrm{L}}_3}{3}, {\mathrm{L}}_{\mathrm{parallel}}={\left(\frac{1}{{\mathrm{L}}_1}+\frac{1}{{\mathrm{L}}_2}+\frac{1}{{\mathrm{L}}_3}\right)}^{-1}$

The magnetic flux linked with a coil (in Wb) is given by the equation 

$\varphi =5t^2+3t+16$

The magnitude of induced emf in the coil at the four-second will be

A and B are two metallic rings placed at opposite sides of an infinitely long straight conducting wire as shown. If current in the wire is slowly decreased, the direction of the induced current will be :

A long solenoid with 15 turns per cm has a small loop of area 2.0 cm² placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from 2.0 A to 4.0 A in 0.1 s, what is the induced emf in the loop while the current is changing?

$$\begin{gathered} \left(1\right) 7.5\times {10}^{-6} V \\ \left(2\right) 6.5\times {10}^{-6} V \\ \left(3\right) 7.5\times {10}^{-5} V \\ \left(4\right) 6.5\times {10}^{-5} V \end{gathered}$$

A circular coil of radius 8.0 cm and 20 turns is rotated about its vertical diameter with an angular speed of 50 rad/s in a uniform horizontal magnetic field of magnitude $3\times {10}^{-2} T.$ The maximum emf induced in the coil is:

A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 ms^-1, at right angle to the horizontal component of the earth's magnetic field, $0.30\times {10}^{-4} Wb m^{-2}$. The instantaneous value of the emf induced in the wire is:

$\begin{array}{rcl}& & 1. 2.5\times {10}^{-3} V\\ & & 2. 1.5\times {10}^{-4} V\\ & & 3. 2.5\times {10}^{-4} V\\ & & 4.1.5\times {10}^{-3} V\end{array}$