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An infinitely long cylinder is kept parallel to an uniform magnetic field B directed along positive Z-axis. This direction of induced current as seen from the Z-axis will be

1) clockwise of the positive Z-axis 2) anti-clockwise of the positive Z-axis 3) zero 4) along the magnetic field Answer: 3) zero... View Article

A copper disc of radius 0.1 m is rotated about its centre with 20 rev/s in a uniform magnetic field of 0.1 T with its plane perpendicular to the field. The emf induced across the radius of the disc is

1) π/20 V 2) 10/π V 3) 20 π mV 4) 10 π mV 5) 2 π mV Answer: 3) 20 π mV Solution: ε = BωR2/2... View Article

The net magnetic flux through any closed surface, kept in a magnetic field is

1) zero 2) μ0/4π 3) 4πμ0 4) 4μ0/π Answer: 1) zero Solution: The net magnetic flux through a closed... View Article

A square coil of side 25 cm having 1000 turns is rotated with an uniform speed in a magnetic field about an axis perpendicular to the direction of the field. At an instant t, the emf induced in the coil is e = 200 sin 100πt. The magnetic induction is

1) 0.50 T 2) 0.02 T 3) 10 -3 T 4) 0.1 T 5) 0.01 T Answer: 5) 0.01 T Solution: e = NBAωSinωt = 200... View Article

A conducting rod of length l is moving in a transverse magnetic field of strength B with velocity v. The resistance of the rod is R. The current in the rod is

1) Blv/R 2) Blv 3) zero 4) B2l2v2/R Answer: 1) Blv/R Solution: The motional emf induced in the conducting rod is given by... View Article

A horizontal straight wire 10 m long extending from East to West is falling with a speed of 5.0 ms^-1 at right angles to the horizontal component of the earth’s magnetic field of strength 0.30 × 10^-4 Wbm^-2. What is the instantaneous value of the emf induced in the wire?

1) + 1.5 × 10-3 Vm-1 2) - 1.5 × 10-3 Vm-1 3) + 1.5 × 10-4 Vm-1 4) - 1.5 × 10-4 Vm-1... View Article

A metal disc of radius 100 cm is rotated at a constant angular speed of 60 rads ^-1 in a plane at right angles to an external field of magnetic induction 0.05 Wbm^-2. The end’ induced between the centre and a point on the rim will be

1) 3 V 2) 1.5 V 3) 6V 4) 9 V Answer: 2) 1.5 VSolution: Given, ω=60rad/s B=0.05Wb/m2 R=100cm=1m Induced emf... View Article

A transformer is often filled with oil. The oil used should have

1) low viscosity 2) high dielectric strength 3) low boiling point 4) high thermal conducting Answer: 2) high dielectric... View Article

If the coefficient of mutual induction of the primary and secondary coils of an induction coil is 5 H and a current of 10 A is cut-off in 5 × 10^-4 s, the emf inducted (in volt) in the secondary coil is

a) 5 x 104 b) 1 x 105 c) 25 x 105 d) 5 x 106 Answer: b) 1 x 105 Solution: Induced emf, e = M(di/dt) = 5 x (10/5 × 10-4)... View Article

The inductance of a coil is L =10 H and resistance R = 5 Ω. If the applied voltage of the battery is 10 V and it switches off in 1 ms, find induced emf of the inductor.

1) 2 × 104 V 2) 1.2 × 104 V 3) 2 × 10-4 V 4) None of these Answer: 1) 2 × 104 V solution: Φ =... View Article

In a step-up transformer, the relation between the number of turns in primary (N_p) and the number of turns in secondary (N_s ) coils is

1) Ns is greater than Np 2) Np is greater than Ns 3) Ns is equal to Np 4) Np = 2Ns Answer: 1) Ns is greater than Np Solution: In... View Article

In a survey of 400 students in a school, 100 were listed as taking apple juice, 150 as taking orange juice and 75 were listed as taking both apple as well as orange juice. Then, which of the following is/are true?

150 students were taking at least one juice. 225 students were taking neither apple juice nor orange juice. (a) Only I is true (b)... View Article

In a group of 500 students, there are 475 students who can speak Hindi and 200 can speak Bengali. What is the number of students who can speak Hindi only?

(a) 275 (b) 300 (c) 325 (d) 350 Solution: Total number of students = 500 Let H be the set showing number of... View Article

A dinner party is to be fixed for a group of 100 persons. In this party, 50 persons do not prefer fish, 60 prefer chicken and 10 do not prefer either chicken or fish. The number of persons who prefer both fish and chicken is.

(a) 20 (b) 22 (c) 25 (d) None of these Solution: Let n(F) denotes the number of persons who prefer fish and n(C) denotes... View Article

If A = {4n + 2| n is a natural number} and B = {3n| n is a natural number}, then what is (A⋂B) equal to?

(a) {12n2 + 6n| n is a natural number} (b) {24n – 12| n is a natural number} (c) {60n + 30| n is a natural number} (d) {12n - 6| n is... View Article

If A and B are subsets of a set X, then what is {A⋂(X-B)}⋃B equal to?

(a) A⋃B (b) A⋂B (c) A (d) B Solution: Given that A and B are subsets of a set X. {A⋂(X-B)}⋃B is the union of A and B.... View Article

Each student in a class of 40, studies at least one of the subjects English, Mathematics and Economics. 16 study English, 22 Economics and 26 Mathematics, 5 study English and Economics, 14 Mathematics and Economics and 2 study all the three subjects. The number of students who study English and Mathematics but not Economics is

(a) 7 (b) 5 (c) 10 (d) 4 Solution: Total number of students = 40 Let x be number of students who study English and Mathematics but not... View Article

If A and B are two sets, then (A – B) ⋃(B – A) ⋃ (A ⋂ B) is equal to

(a) Only A (b) A ⋃ B (c) (A⋃B)’ (d) None of these Solution: (A - B) ⋃(B - A) ⋃ (A ⋂ B) = only A ⋃ only B ⋃ both A and... View Article

If A, B, C are three sets, then what is A – (B – C) equal to?

(a) A - (B ⋂ C) (b) (A - B) ⋃ C (c) (A - B) ⋃ (A ⋂ C) (d) (A - B) ⋃ (A - C) Solution: Image will be uploaded soon. Following Venn diagram... View Article

Let S = the set of all triangles, P = the set of all isosceles triangles, Q = the set of all equilateral triangles, R = the set of all right-angled triangles. What do the sets P ⋂ Q and R – P represents respectively?

(a) The set of isosceles triangles; the set of non- isosceles right-angled triangles (b) The set of isosceles triangles; the set of... View Article