The synchronous motor is cheaper than 3 phase induction motor for which condition: High speed, low output High speed, High output Low speed, High output All of these Correct answer: 3. Low speed, High output Explanation: Under the subject conditon the induction motors use large amount of iron so that air flux density doesn’t exceed … Read more
Permanent magnet moving coil instrument can be used for: AC DC Both of these None of these Correct answer: 2. DC only Since the alternating current varies with time, this variation of current also changes the torque of coil. However, the pointer of PMMC can’t keep on fast reverse and is thus not suitable enough … Read more
In real transformers, the percentage of copper losses account for how much of the total losses: 20% 55% 85% 98.5% Correct answer: 3. 85% In real transformers, the percentage of copper losses account for 85% of the total losses.
The efficiency of the transformer is maximum when: Resistance of primary equals secondary Copper losses equal iron losses When leakage reactance of primary equals secondary None of these Correct answer: 2. Copper losses equal iron losses The efficiency of transformer is maximum when copper losses equals the iron losses.
If the frequency of 3-phase supply to an induction motor is increased, the synchronous speed will: Decrease Increase Remain same as before None of these Correct answer: 2. Increase
As compared to the solid conductor, a stranded conductor has: More corona Less corona Same corona None of these Correct answer: 1. More corona Corona effect depends on the shape of the conductor. An irregular shape (such as a stranded conductor) has more corona as compare to the solid conductor.
In Distribution Transformers the protection devices are provided on: L.T side only H.T side only Both of these None of these Correct answer: 3. Both of these In distribution transformer, the protection devices are provided on both H.T and L.T sides.
If the length of the cable increases its capacitance: Increases Decreases Remains the same None of these Correct answer: 1. Increases By increasing length the capacitance of cable also increases.
Earth wire in overhead transmission lines: Increases line inductance Decreases line inductance Increases line capacitance Decreases line capacitance Correct answer: 3. Increase line capacitance The presence of earth wire in overhead transmission lines causes the line capacitance to increase.
Ferranti Effect is best defined as: The phenomenon of violet glow, hissing noise, and production of ozone gas The tendency of alternating current to concentrate near the surface of a conductor The increase in voltage at the receiving end of AC transmission lines The difference in level between points of supports and the lowest point … Read more