1. Which of the following does not change in a transformer ? (a) Current (b) Voltage (c) Frequency (d) All of the above Ans: c 2. In a transformer the energy is conveyed from primary to secondary (a) through cooling coil (b) through air (c) by the flux (d) none of the above Ans: c
1. Laminations of core are generally made of (a) case iron (b) carbon (c) silicon steel (d) stainless steel Ans: c 2. Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ? (a) 0.005 mm (b) 0.05 mm (c) 0.5 m (d) 5 m Ans:
1. A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second. (a) 100 n (b) 50 jt (c) 25 JT (d) 5 n Ans: a 2. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance
1. The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as (a) self-inductance (b) mutual inductance (c) series aiding inductance (d) capacitance Ans: a 2. As per Faraday’s laws of electromagnetic induction, an e.m.f. is induced in a
1. Tesla is a unit of (a) field strength (b) inductance (c) flux density (d) flux Ans: c 2. A permeable substance is one (a) which is a good conductor (6) which is a bad conductor (c) which is a strong magnet (d) through which the magnetic lines of force can
1. The S.I. unit of power is (a) Henry (b) coulomb (c) watt (d) watt-hour Ans: c 2. Electric pressure is also called (a) resistance (b) power (c) voltage (d) energy Ans: c 3. The substances which have a large number of free electrons and offer a low resistance are called (a) insulators
1. The force between two charges is 120 N. If the distance between the charges is doubled, the force will be (a) 60 N (b) 30 N (c) 40 N (d) 15 N Ans: b 2. The electric field intensity at a point situated 4 meters from a point charge is 200 N/C. If the
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