Basic Electrical Engineering Interview Questions

Q.1 What does 10V AC mean? Is it the RMS voltage or Peak voltage or Average voltage?

Answer. In general, AC voltages and currents are mentioned in RMS values only. It is sensible to compare with steady DC voltages and currents.
For example 230V AC supply means, 230Vrms AC Supply.

Q.2 What does the Voltmeter in AC mode show? Is it RMS value or peak value?

Answer. Multimeter in AC mode shows RMS value of the voltage or current. Also when it is DC mode it will show the RMS value only.

Q.3 Can fuses with an AC voltage rating be used in a DC applications?

Answer: Fuses must be rated for the voltage AC or DC in which they will be used. Generally, fuses have a DC voltage rating that is half of the maximum AC voltage rating.

Q.4 Why in a three pin plug the earth pin is thicker and longer than the other pins?

Answer: It depends upon R=ρL/A where area (A) is inversely proportional to resistance (R), so if area (A) increases, R decreases & if R is less the leakage current will take low resistance path so the earth pin should be thicker. It is longer because the The First to make the connection and last to disconnect should be earth Pin. This assures Safety for the person who uses the electrical instrument.

Q.5 Why humming sound occurred in HT transmission line?

Answer: This sound is coming due to ionization (breakdown of air into charged particles) of air around transmission conductor. This effect is called as Corona effect, and it is considered as power loss.

Q.6 What the main difference between UPS & inverter?

Answer: Uninterrupted power supply is mainly use for short time. Means according to ups VA it gives backup. Ups is also two types: on line and offline. Online ups having high volt and amp for long time backup with high dc voltage. But ups start with 12v dc with 7 amps. but inverter is start with 12v,24,dc to 36v dc and 120amp to 180amp battery with long time backup

Q.7 Why the capacitors work on ac only?

Answer: Generally capacitor gives infinite resistance to dc components (i.e., block the dc components). It allows the ac components to pass through.

Q.8 Why We use of Stones/Gravel in electrical Switch Yard

Answer: Reducing Step and Touch potentials during Short Circuit Faults Eliminates the growth of weeds and small plants in the yard Improves yard working condition Protects from fire which cause due to oil spillage from transformer and also protects from wild habitat.