MCQ 1 SF6 gas ___________.

(A) has pungent small (B) is yellow in colour (C) is nontoxic (D) is lighter than air

MCQ 2 The main function of a fuse ________________.

(A) protect the appliance (B) prevent excessive currents (C) open the circuit (D) protect the line

MCQ 3 Which of the following medium is employed for extinction of arc in air circuit breaker

(A) Mineral Oil (B) Water (C) SF6 (D) Air

MCQ 4 The arcing contacts in a circuit breaker are made of

(A) Copper tungsten alloy (B) Magnine (C) Aluminium alloy (D) Nichrom

MCQ 5 With which of the following, a circuit breaker must be equipped for remote operation ___________.

(A) Shunt trip (B) Time-delay trip (C) Inverse time trip (D) All are correct

MCQ 6 Fault diverters are basically _____________.

(A) SF6 circuit breakers (B) fast switches (C) contactors (D) Relays

MCQ 7 Thermal circuit breaker has a

(A) delayed trip action (B) instantaneous trip action (C) both  (A) and (B) (D) None is correct

MCQ 8 D.C. shunt relays are made of

(A) few turns of thin wire (B) many turns of thin wire (C) many turns of thick wire (D) few turns of thick wire

MCQ 9 An efficient arid a well designed protective relaying should have

(A) high speed and selectivity (B) economy and simplicity (C) good selectivity and reliability (D) All of the above

MCQ 10 Ionization in circuit breaker is facilitated by ____________

(A) increase of mean free path (B) increasing field strength (C) high temperature (D) all of the above

MCQ 11 In a circuit breaker the basic problem is to à

(A) transmit large power (B) emit the ionizing electrons (C) maintain the arc (D) extinguish the arc

MCQ 12 A differential relay measures the vector difference between

(A) two voltages (B) two currents (C) two or more similar electrical quantities (D) all of the above

MCQ 13 Overload relays are of ____________ type.

(A) Electromagnetic (B) Induction (C) Solid state (D) All are correct

MCQ 14 Circuit breakers are essentially ______________.

(A) Current carrying contacts called electrodes (B) arc extinguishers (C) circuits to break the system (D) transformers to isolate the two systems

MCQ 15 Overheating of relay contacts or contact born out is due to

(A) foreign matter on the contact surface (B) slow making and breaking of load circuit contacts (C) too low contact pressure (D) All are correct

MCQ 16 Burden of a protective relay is the power

(A) absorbed by the circuit of relay (B) required to operate the circuit breaker (C) developed by the relay circuit (D) All are correct

MCQ 17 Shunt capacitance is neglected while considering

(A) Medium transmission line (B) Long transmission line (C) Short transmission line (D) Medium and long transmission lines

MCQ 18 In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

(A) be of sufficient size and proper shape (B) be clean and smooth (C) have low contact resistance (D) All are correct

MCQ 19 Thermal overload relays are used to protect the motor against over current due to

(A) short-circuits (B) heavy loads (C) ground (D) None is correct

MCQ 20 Arc in a circuit behaves as ___________.

(A) resistance increasing with voltage rise across the arc (B) capactive reactance (C) inductive reactance (D) a resistance decreasing with voltage rise across the arc

MCQ 21 Relays can be designed to respond to changes in

(A) voltage and current (B) resistance, reactance or impedance (C) light intensity and temperature (D) All are correct

MCQ 22 A thermal protection switch can protect against __________.

(A) overload current (B) over voltage (C) short-circuit (D) temperature

MCQ 23 Directional relays are based on flow of ____________.

(A) power (B) current (C) voltage (D) All are correct

MCQ 24 The ground wire should not be smaller than No _______ copper.

(A) 7 (B) 8 (C) 9 (D) 10

MCQ 25 H.R.C. fuses provide best protection against

(A) short-circuits (B) overload (C) reverse current (D) None is correct