MCQs

The use of higher flux density in the transformer design: Reduces weight per kva Reduces iron losses Reduces copper losses Increases part load efficiency Correct answer: 1. Reduces weight per kVA

Which of the following is the main advantage of an auto-transformer over a two winding transformer: Elimination of Eddy current losses Copper losses are negligible Saving in winding material Reduced Hysteresis losses Correct answer: 3. Saving in winding material

The full-load copper loss of a transformer is 3200 W. At half-load the copper loss will be: 6400 W 1600 W 800 W 400 W Correct answer: 3. 800 W Explanation: Copper losses = I2 R At half load the current becomes half Copper losses at half load = (I/2)2 R = I2/4 . R … Read more

The main reason for the generation of harmonics in a transformer could be: Fluctuating load Poor insulation Mechanical vibrations Saturation of core Correct answer: 4. Saturation of core

The unit of conductivity is Ω mho mho/m ohm/m Correct answer: 3. mho/m

The correct formula to calculate voltage is: V = WI V = P/R V = W/Q V = I.t Correct answer: 3. V = W/Q By definition the voltage is 1 volt if one joule of energy is required to move one coulomb of charge from one point to the other.

The Correct Formula for Ohm’s Law is: V = IR V = R/I V = I/R V = P/R Correct answer: V = IR According to Ohm’s law the electrical current in any circuit is directly proportional to the resistance. V ∝ I OR The voltage through any resistor is directly proportional to the product … Read more

The essential property which should be present in transformers breather chemical is: Ionizing air Absorbing moisture Higher level of oxygen Cooling the transformer oil Correct answer: 2. Absorbing moisture

The noise resulting from vibrations of laminations set by magnetic force, is termed as: Magnetostriction Humming Stalling Crimping Correct answer: 2. Humming