If n (A) = 115, n (B) = 326, n (A – B) = 47, then what is n(A⋃B) equal to?
(a) 373 (b) 165 (c) 370 (d) 394 Solution: We know, for two sets A and B A – B... View Article
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If A, B, and C are three finite sets, then what is [(A⋃B) ⋂ C]’ equal to?
(a) A’⋃B’ ⋂ C’ (b) A’⋂B’⋂C’ (c) A’⋂B’⋃C’ (d) A⋂B⋂C Solution: [(A⋃B) ⋂ C]’ = (A⋃B)’ ⋃ C’ = (A’⋂B’... View Article
Consider the following statements: For non empty sets A, B and C
Consider the following statements: For non empty sets A, B and C. 1. A – ( B – C) =... View Article
If m is the universal set and P is a subset of m, then what is P ⋂ ((P-m) ⋃ (m -P)) equal to?
(a) Ø (b) P’ (c) m (d) P Solution: Given that m is the universal set and P is a... View Article
If F(n) denotes the set of all divisors of n except 1, what is the least value of y satisfying [F(20) ⋂ F(16)] ⊆ F(y)?
(a) 1 (b) 2 (c) 4 (d) 8 Solution: F(n) denotes the set of all divisors of n except 1.... View Article
Which types of losses do not occur in the transformer?
1) Iron losses 2) Copper losses 3) Mechanical losses 4) Flux leakage Answer: 3) Mechanical losses Solution: Iron losses:- In actual... View Article
In the transmission of a.c. power through transmission lines, when the voltage is shaped up n times, the power loss in transmission,
1) increase n times 2) Decrease n times 3) Increase n2 times 4) Decrease n2 times Answer: 4) Decrease n2 times Solution:... View Article
Two different loops are concentric & lie in the same plane. The current in outer loop is clockwise & increasing with time. The induced current in the inner loop then, is……….
1) clockwise 2) zero 3) counter clockwise 4) direction depends on the ratio of loop radii Answer: 3) counter clockwise Solution:... View Article
The induction coil works on the principle of
1) self induction 2) mutual induction 3) Ampere’s rule 4) Flemidg’s right hand rule Answer: 2) mutual induction Solution: Induction coil... View Article
A solenoid 600 mm long has 50 turns on it and is wound on an iron rod of 7.5 mm radius. Find the flux through the solenoid when the current in it, is 3A. The relative permeability of iron is 600.
1) 1.66 Wb 2) 1.66 nWb 3) 1.66 mWb 4) 1.66 μWb 5) 1.66 pWb Answer: 3) 1.66 mWb Solution: r... View Article
The energy stored in an inductor of self inductance L henry carrying a current of 1 A is
1) L2I 2) -LI2 3) (½) LI2 4) (½)L2I Answer: 3) (½) LI2 Solution: Voltage across inductor, V = L (di/dt)... View Article
A solenoid 30 cm long is made by winding 2000 loops of wire on an iron rod whose cross-section is 1.5 cm2. If the relative permeability of the iron is 6000. What is the self inductance of the solenoid?
1) 15 H 2) 2.5 H 3) 3.5 H 4) 0.5 H Answer: 1) 15 H Solution: Self – inductance of... View Article
Two coils have a mutual inductance 5 mH. The current changes in the first coil according to equation I = I0 sin ωt, where, I0 =10 A and ω =100 π rad /s. The maximum value of emf in the second coil is
1) 2π 2) 5π 3) π 4) 4π Answer: 2) 5π Solution: ε = M(dI/dt) = Md(I0sinωt)/dt = MI0ωcosωt = (5... View Article
The magnitude of the earth’s magnetic field at a place is B0 and the angle of dip is δ. A horizontal conductor of length l lying magnetic North South moves Eastwards with a velocity v, the emf induced across the conductor is
1) zero 2) B0 lv sin δ 3) B0 lv 4) B0 lv cos δ 5) B0 sin δ Answer: 2)... View Article
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)... 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... 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 surface will be zero,... 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:... 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... 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 Answer: 1)... View Article
