Balbharati solutions for Physics [English] 12 Standard HSC Maharashtra State Board chapter 12 - Electromagnetic induction [Latest edition]

A circular coil of 100 turns with a cross-sectional area of 1 m² is kept with its plane perpendicular to the magnetic field of 1 T. The magnetic flux linkage is ______.

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A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?

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Two inductor coils with inductance 10 mH and 20 mH are connected in series. What is the resultant inductance of the combination of the two coils?

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A current through a coil of self-inductance 10 mH increases from 0 to 1 A in 0.1 s. What is the induced emf in the coil?

What is the energy required to build up current of 1A in an inductor of 20 mH?

What is electromagnetic induction?

State Faraday's laws of electromagnetic induction.

State and explain Lenz’s law in light of the principle of conservation of energy.

What are eddy currents?

State applications of eddy currents.

Answer in brief:

If a copper disc swings between the poles of a magnet, the pendulum comes to rest very quickly. Explain the reason. What happens to the mechanical energy of the pendulum?

Explain why the inductance of two coils connected in parallel is less than the inductance of either coil.

In a Faraday disc dynamo, a metal disc of radius R rotates with an angular velocity ω about an axis perpendicular to the plane of the disc and passing through its center. The disc is placed in a magnetic field B acting perpendicular to the plane of the disc. Determine the induced emf between the rim and the axis of the disc.

A horizontal wire 20 m long extending from east to west is falling with a velocity of 10 m/s normal to the Earth’s magnetic field of 0.5 × 10⁻⁴ T. What is the value of induced emf in the wire?

A metal disc of radius 30 cm spins at 20 revolution per second about its transverse symmetry axis in a uniform magnetic field of 0.20 T. The field is parallel to the axis of rotation. Calculate
(a) the area swept out per second by the radius of the disc
(b) the flux cut per second by a radius of the disc
(c) the induced emf between the axle and rim of the disc.

A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 10 A in 0.2 s, what is the change of flux linkage with the other coil?

A long solenoid has turns per unit length 1.5 x 10³ per meter and area of cross-section 25 cm². A coil C of 150 turns is wound tightly around the center of the solenoid. For a current of 3 A in the solenoid, calculate
(a) the magnetic flux density at the centre of the solenoid
(b) the flux linkage in the coil C
(c) the average emf induced in coil C if the current in the solenoid is reversed in the direction in a time of 0.5 s. [µ₀ = 4π x 10^-7 H/m]

A search coil having 2000 turns with area 1.5 cm² is placed in a magnetic field of 0.60 T. The coil is moved rapidly out of the field in a time of 0.2 s. Calculate the induced emf in the search coil.

An aircraft of wing span of 50 m flies horizontally in the Earth's magnetic field of 6 x 10^-5 T at a speed of 400 m/s. Calculate the emf generated between the tips of the wings of the aircraft.

A stiff semi-circular wire of radius R is rotated in a uniform magnetic field B about an axis passing through its ends. If the frequency of rotation of wire is f, calculate the amplitude of alternating emf induced in the wire.

Calculate the induced emf between the ends of an axle of a railway carriage 1.75 m long traveling on level ground with a uniform velocity of 50 kmph. The vertical component of Earth's magnetic field (B_v) is 5 × 10^-5 T. 

The mutual inductance of two coils is 10 mH. If the current in one of the coil changes from 5 A to 1 A in 0.2 s, calculate the emf induced in the other coil. Also calculate the induced charge flowing through the coil if its resistance is 5 Ω.

An emf of 96.0 mV is induced in the windings of a coil when the current in a nearby coil is increasing at the rate of 1.20 A/s. What is the mutual inductance (M) of the two coils?

A long solenoid of length l, cross-sectional area A and having N₁ turns (primary coil), has a small coil of N₂ turns (secondary coil) wound about its center. Determine the Mutual inductance (M) of the two coils.

The primary and secondary coils of a transformer each have an inductance of 200 x 10^-6 H. The mutual inductance between the windings is 4 x 10^-6 H. What percentage of the flux from one coil reaches the other?

A toroidal ring made from a bar, of length 1 m and diameter 1 cm, bent into a circle. It is wound tightly with 100 turns per centimeter. If the permeability of the bar is equal to that of free space, calculate
(a) the magnetic field inside the bar when the current through the turns is 100 A
(b) the self-inductance of the coil.

A uniform magnetic field B(t), pointing upward fills a circular region of radius, s in a horizontal plane. If B is changing with time, find the induced electric field.