Download Aptitude Crack
img not found img not found

Signals and Switches - Technical MCQs

Q1:

A diode placed in parallel across a relay coil serves what function?

A to regulate input voltage

B to protect the coil from arcing

C to ensure most of the current passes through the coil

D to reduce arcing across the relay contacts

ANS:B - to protect the coil from arcing

During opening of current carrying contacts in a circuit breaker the medium in between opening contacts become highly ionized through which the interrupting current gets low resistive path and continues to flow through this path even the contacts are physically separated. During the flowing of current from one contact to another the path becomes so heated that it glows. This is called arc.