Physics NCERT Exemplar Solutions Class 12th Chapter Six Electromagnetic Induction

There are two coils A and B separated by some distance. If a current of 2 A flows through A, a magnetic flux of 10^-2Wb passes through B (no current through B). If no current passes through A and a current of 1A passes through B, what is the flux through A ?

A magnetic field in a certain region is given by B = B_ocos(ωt) k and a coil of radius a with resistance R is placed in the x-y plane with its centre at the origin in the magnetic field. Find the magnitude and the direction of the current at (a, 0, 0) at t = π/2ω, t = π/ω and t = 3π/2ω

Consider a closed loop C in a magnetic field (figure). The flux passing through the loop is defined by choosing a surface whose edge coincides with the loop and using the formula ? = B₁dA₁, B₂dA₂…. Now, if we choose two different surfaces S₁ and S₂ having C as their edge, would we get the same answer for flux. Justify your answer.

A magnetic field B = B₀sin (ωt)k covers a large region where a wire AB slides smoothly over two parallel conductors separated by a distance d (figure). The wires are in the x-y plane. The wire AB (of length d) has resistance R and the parallel wires have negligible resistance. If AB is moving with velocity v, what is the current in the circuit. What is the force needed to keep the wire moving at constant velocity?

A conducting wire XY of mass m and negligible resistance slides smoothly on two parallel conducting wires as shown in figure. The closed circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field B = B(t) k

(i) Write down an equation for the acceleration of the wire XY

(ii) If B is independent of time, obtain v(t), assuming v(0) = u₀

(iii) For (ii), show that the decrease in kinetic energy of XY equals the heat lost in

ODBAC is fixed rectangular conductor of negligible resistance (CO is not connected) and OP is a conductor which rotates clockwise with an angular ve1locity omega Fig. The entire system is in a uniform magnetic field B whose direction in along the normal to the surface of the rectangular conductor ABDC. The conductor OP is in electric contact with ABDC. The rotating conductor has a resistance of  per unit length. Find the current in the rotating conductor, as it rotates by 180

A square of side L meters lies in the x-y plane in a region, where the magnetic field is given by B=B₀(2i+3j+4k)T, where Bo is constant. The magnitude of flux passing through the square is

(a) 2 Bo L²

(b) 3 Bo L² Wb

(c) 4 Bo L² Wb

(d) B₀L² Wb

A loop, made of straight edges has six corners at A(0,0,0),B(L,0,0),C(L,L,O),D(0,L,0),E(0,L,L)and F(0,0,L). A magnetic field B =B_o(i+K)T is present in the region. The flux passing through the loop ABCDEFA (in that order) is

A cylindrical bar magnet is Rotated about its axis. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then,

(a) A direct current flows in the ammeter A

(b) No current flows through the ammeter A

(c) An alternating sinusoidal current flows through the ammeter A with a time period 2π/ω

(d) A time varying non-sinusoidal current flows through the ammeter A

Consider a magnet surrounded by a wire, with an on/off switch S (figure). If the switch is thrown from the off position (open circuit) to the on position (closed circuit), will a current flow in the circuit? Explain

A wire in the form of a tightly wound solenoid is connected to a DC source, and carries a current. If the coil is stretched so that there are gaps between successive elements of the spiral coil, will the current increase or decrease? Explain.

A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, will the current increase or decrease? Explain.

An expression for a dimensionless quantity P is given by $P=\frac{\alpha }{\beta }lo{g}_e\left(\frac{kt}{\beta t}\right);$ where α and β are constants, x is distance; k is Boltzmann constant and t is the temperature. Then the dimensions of will be

A thin circular ring of mass M and radius R is rotating with a constant angular velocity 2 rads^-1 in a horizontal plane about an axis vertical to its plane and passing through the centre of the ring. If two objects each of mass m be attached gently to the opposite ends of a diameter of ring, the will then rotate with an angular velocity (in rads^-1).

The variation of acceleration due to gravity (g) with distance (r) from the centre of the earth is correctly represented by: (Given R = radius of earth)

Two small spheres each of mass 10mg are suspended from a point by threads 0.5m long. They are equally charged and repel each other to a distance of 0.20m. The charge on each of the sphere is $\frac{a}{21}\times 10^{-8}C.$  The value of ‘a’ will be…….. [Given g = 10 ms^-2]

Two particles having masses 4g and 16g respectively are moving with equal kinetic energies. The ratio of the magnitudes of their linear momentum is n : 2. The value of n will be………..

A reversible heat engine converts one-fourth of the heat input into work. When the temperature of the sink is reduced by 52K, its efficiency is doubled. The temperature is Kelvin of the source will be…………