1. Which of the following are necessary conditions for an entire 3-phase system to be balanced? The line voltages are equal in magnitude. The phase differences between successive line voltages are equal. The impedances in each of the phases are identical. Select the correct answer using the codes given below: (a) 1, 2 and 3 […]
1. When a sinusoidal voltage is applied across R – L series circuit having R = XL, the phase angle will be (a) 90o (b) 45o lag (c) 45o leading (d) 90o leading 2. An ac source of 200 V RMS supplies active power of 600 W and reactive power of 800 VAR. The RMS
1. The magnetic susceptibility of a paramagnetic material is (a) less than zero (b) less than one but positive (c) greater than one (d) equal to zero 2. Air exhibits (a) ferromagnetism (b) paramagnetism (c) antiferromagnetism 3. Soft magnetic materials have (a) high permeability and low coercive force (b) low permeability and high coercive force
1. Internal resistance of primary cell varies (a) inversely with the distance between electrodes (b) inversely with the surface area of electrodes (c) directly with the distance between electrodes (d) with the nature of electrodes (e) all of above except (a) 2. If the battery has zero internal resistance and the external resistance R is
1. Ohm’s law cannot be applied to the circuits consisting of (a) electronic tubes or transistors (b) non-linear elements (c) powdered iron, electric arc etc. (d) all of the above. An electric circuit, whose characteristics or properties are same in either direction (e.g. a distribution or transmission line) is called the bilateral circuit. An electric
1. The specific energy consumption of a train depends on which of the following? (a) Acceleration and retardation (b) Gradient (c) Distance covered (d) All of the above 2. The friction at the track is proportional to (a) 1/speed (b) speed (c) 1/speed2 (d) none of the above 3. The air resistance to the movement
1. The travelling speed of cranes varies from (a) 20 to 30 m/s (b) 10 to 15 m/s (c) 5 to 10 m/s (d) 1 to 2.5 m/s 2. Which of the following motors is preferred when quick speed reversal is the main consideration ? (a) Squirrel cage induction motor (b) Wound rotor induction motor
1. Which of the following motors always starts on load ? (a) Conveyor motor (b) Floor mill motor (c) Fan motor (d) All of the above 2. ……….. is preferred for automatic drives. (a) Squirrel cage induction motor (b) Synchronous motors (c) Ward-Leonard controlled D.C. motors (d) Any of the above 3. When the load
1. Between Field’s test and Hopkinson’s test the main common thing is that both (a) use negligible power (b) are regenerative tests (c) need two similar mechanically coupled motors (d) need two electrically coupled series motors 2. The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes
1. The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is (a) 2.36% (b) 4.76% (c) 6.71% (d) 8.84% 2. The armature voltage control of D.C. motor provides (a) constant torque drive (b) constant voltage drive (c) constant current drive (d)