STANDARD Physics Electromagnetic Induction Class 12 Questions

Which of the following options is true?

The magnetic flux linked with a coil of N turns of area of cross section A held with its plane parallel to the field B is

A circular disc of radius 0.2 m is placed in a uniform magnetic field of induction \( \frac{1}{\pi} \) Wb m⁻² in such a way that its axis makes an angle of 60° with B. The magnetic flux linked with the disc is

A coil of area 0.4 m² has 100 turns. A magnetic field of 0.04 Wb m⁻² is acting normal to the coil surface. If this magnetic field is reduced to zero in 0.01 s, then the induced emf in the coil is

A square of side x m lies in the x-y plane in a region, where the magnetic field is given by B = B₀(3i + 4j + 5k)T, taking B₀ as constant. The magnitude of flux passing through the square is

The magnetic flux through a coil perpendicular to its plane and directed into paper is varying according to the relation ϕ = (2t² + 4t + 6) mWb. The emf induced in the loop at t = 4 s is

A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s⁻¹. The induced emf when the radius is 2 cm, is

A rectangular coil of 100 turns and size 0.1 m × 0.05 m is placed perpendicular to a magnetic field of 0.2 T. If the field drops to 0.05 T in 0.05 second, the magnitude of the e.m.f. induced in the coil is

A closed iron ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is

Lenz’s law is a consequence of the law of conservation of

A metallic ring is attached with the wall of a room. When the north pole of a magnet is brought near it, the induced current in the ring will be

A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when :

According to Lenz's law of electromagnetic induction

The Capacitive reactance & inductive reactance in DC supply is ?

The direction of induced current in the right loop in the situation shown by the given figure is

When an iron core is inserted into the solenoid, the current will

Which of the following statements is not correct?

In the given figure, current from A to B in the straight wire is decreasing. The direction of induced current in the loop is

The variation of induced emf (ε) with time (t) in a coil if a short bar magnet is moved along its axis with a constant velocity is best represented as

The north pole of a bar magnet is rapidly introduced into a solenoid at one end (say A). Which of the following statements correctly depicts the phenomenon taking place?

As shown in the figure, a metal rod makes contact with a partial circuit and completes the circuit. The circuit area is perpendicular to a magnetic field with B = 0.15 T. If the resistance of the total circuit is 3 Ω, the force needed to move the rod as indicated with a constant speed of 2 m s⁻¹ will be equal to

A circuit area 0.01 m² is kept inside a magnetic field which is normal to its plane. The magnetic field changes from 2 tesla to 1 tesla in 1 millisecond. If the resistance of the circuit is 2 Ω, the rate of heat evolved is

The coefficient of mutual inductance of two coils depends on

Two circular coils can be arranged in any of three situations as shown in the figure. Their mutual inductance will be

A pair of adjacent coils has a mutual inductance of 2.5 H. If the current in one coil changes from 0 to 40 A in 0.8 s, then the change in flux linked with the other coil is

If number of turns in primary and secondary coils is increased to two times each, the mutual inductance

A short solenoid of radius a, number of turns per unit length n₁, and length L is kept coaxially inside a very long solenoid of radius b, number of turns per unit length n₂. What is the mutual inductance of the system?

A 2 m long solenoid with diameter 2 cm and 2000 turns has a secondary coil of 1000 turns wound closely near its midpoint. The mutual inductance between the two coils is

A solenoid of length 30 cm with 10 turns per centimetre and area of cross-section 40 cm² completely surrounds another co-axial solenoid of same length, area of cross-section 20 cm² with 40 turns per centimetre. The mutual inductance of the system is

Two conducting circular loops of radii R₁ and R₂ are placed in the same plane with their centres coinciding. If R₁ > R₂, the mutual inductance M between them will be directly proportional to

The self inductance of a long solenoid cannot be increased by

If the current sensitivity of a galvanometer is doubled, then its voltage sensitivity will be

The self inductance of a coil having 400 turns is 10 mH. The magnetic flux through the cross section of the coil corresponding to current 2 mA is

Two moving coil metres M₁ and M₂ have the following particulars R₁ = 10Ω; N₁ = 30; A₁ = 3.6 × 10⁻³ m²; B₁ = 0.25T; R₂ = 14Ω; N₂ = 42; A₂ = 1.8 × 10⁻³ m²; B₂ = 0.50T. The spring constants are identical for the two metres. What is the ratio of current sensitivity and voltage sensitivity of M₂ to M₁?

In a coil current falls from 5 A to 0 A in 0.2 s. If an average emf of 150 V is induced, then the self inductance of the coil is

Two coils of self-inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils are

If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will

Two solenoids of equal number of turns have their lengths and the radii in the same ratio 1 : 2. The ratio of their self inductances will be

A transformer works on the principle of

For an ideal step-down transformer, the quantity which is constant for both the coils is

By a change of current from 5 A to 10 A in 0.1s, the self induced emf is 10 V. The change in the energy of the magnetic field of a coil will be

A boy peddles a stationary bicycle the pedals of the bicycle are attached to a 400 turn coil of area 0.20 m². The coil rotates at one fourth of a revolution per second and it is placed in a uniform magnetic field of 0.05 T perpendicular to the axis of rotation of the coil. The maximum voltage generated in the coil is

The core of a transformer is laminated to reduce

The self inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as

Assertion : Mutual inductance of a pair of coils depend on their separation as well as their relative orientation. Reason : Mutual inductance depend upon the length of the coil only.

The loss of energy in the form of heat in the iron core of a transformer is

A circular ring of diameter 20 cm has a resistance of 0.01 Ω. The charge that will flow through the ring if it is turned from a position perpendicular to a uniform magnetic field of 2.0 T to a position parallel to the field is about

A transformer is used to light 140 W, 24 V lamp from a 240 V ac mains. If the main current is 0.7 A, the efficiency of the transformer is

A 10 m long horizontal wire extends from north-east to south-west. It is falling with a speed of 5.0 m s⁻¹, at right angles to the horizontal component of the earth's magnetic field of 0.3 × 10⁻⁴ Wb/m². The value of the induced emf in wire is

The primary of a transformer when connected to a dc battery of 10 volt draws a current of 1 mA. The number of turns of the primary and secondary windings are 50 and 100 respectively. The voltage in the secondary and the current drawn by the circuit in the secondary are respectively