INTERESTING QUESTIONS ANS ANSWER-1

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

ANS:

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.

2. What is the difference between MCB & MCCB, Where it can be used?

ANS:

MCB is miniature circuit breaker which is thermal operated and use for short circuit protection in small current rating circuit.

Normally it is used where normal current is less than 100A.

MCCB moulded case circuit breaker and is thermal operated for over load current and magnetic operation for instant trip in short circuit condition. Under voltage and under frequency may be inbuilt.

Normally it is used where normal current is more than 100A.

3. Why Delta Star Transformers are used for Lighting Loads?

ANS:

For lighting loads, neutral conductor is must and hence the secondary must be star winding and this lighting load is always unbalanced in all three phases.
To minimize the current unbalance in the primary we use delta winding in the primary So delta / star transformer is used for lighting loads.