Practice Test: Question Set - 03
1. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring
- (A) Current during abnormal condition
- (B) Voltage during abnormal condition
- (C) Constantly the electrical quantities which
differ during normal and abnormal conditions
- (D) None of the above
2. Overheating of relay contacts or contact born out is due to
- (A) Slow making and breaking of load circuit
contacts
- (B) Foreign matter on the contact surface
- (C) Too low contact pressure
- (D) All of the above
3. An efficient and a well designed protective relaying should have
- (A) Good selectivity and reliability
- (B) Economy and simplicity
- (C) High speed and selectivity
- (D) All of the above
4. D.C. shunt relays are made of
- (A) Few turns of thin wire
- (B) Few turns of thick wire
- (C) Many turns of thin wire
- (D) Many turns of thick wire
5. Arc in a circuit behaves as
- (A) A capacitive reactance
- (B) An inductive reactance
- (C) A resistance increasing with voltage rise
across the arc
- (D) A resistance decreasing with voltage rise
across the arc
6. The main function of a fuse is to
- (A) Protect the line
- (B) Open the circuit
- (C) Protect the appliance
- (D) Prevent excessive currents
7. The current zero interruption, in oil and air blast circuit breakers, is achieved by
- (A) Lengthening of the gap
- (B) Cooling and blast effect
- (C) Both (A) and (B)
- (D) Deionising the oil with forced air
8. Ionization in circuit breaker is facilitated by
- (A) High temperature
- (B) Increase of mean free path
- (C) Increasing field strength
- (D) All of the above
9. The delay fuses are used for the protection of ________.
- (A) Motors
- (B) Power outlet circuits
- (C) Fluorescent lamps
- (D) Light circuits
10. When a wave propagates on a transmission line, it suffers reflection several times at
- (A) Tapping
- (B) Load end
- (C) Sending end
- (D) Sending and other end
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