Power Electronics MCQ #1
1) A triac is equivalent to two SCRs …………..
A) In parallel
B) In series
C) In inverse-parallel
D) None of the above
2) A DIAC has ………….. terminals
A) Two
B) Three
C) Four
D) None of the above
3) The device that does not have the gate terminal is ……………….
A) Triac
B) FET
C) SCR
D) DIAC
4) A diac is turned on by …………………
A) A breakover voltage
B) Gate voltage
C) Gate current
D) None of the above
5) A diac is simply ………………
A) A single junction device
B) A three junction device
C) A triac without gate terminal
D) None of the above
6) In a SCR,
A) Gate current is directly proportional to forward breakover voltage
B) As gate current is raised, forward breakover voltage reduces
C) Gate current has to be kept on continuously for conduction
D) Forward break-over voltage is low in the forward blocking state.
7) When a SCR is in the forward blocking state,
A) All the 3 junctions are reverse biased
B) The anode and cathode junctions are forward biased but the gate junction is reverse biased
C) The anode junction is forward biased but the cathode and gate junctions are reverse biased
D) The anode and gate junctions are forward biased but the cathode junction is reverse biased
8) A fully controlled thyristor bridge drives a DC motor. The system is capable of
A) Motoring and braking in both directions
B) Only motoring in both directions, no braking
C) Motoring in forward direction and braking in reverse direction
D) Only motoring in forward direction, no braking
9) During forward blocking state, the SCR has
A) Low current, medium voltage
B) Low current, large voltage
C) Medium current, large voltage
D) Large current, low voltage
10) The SCR can be termed as
A) DC switch
B) AC switch
C) Square-wave switch
D) Either A or B
| (1)-C | (2)-A | (3)-D | (4)-A | (5)-C | (6)-B | (7)-B | (8)-D | (9)-B | (10)-A |
11) In a thyristor, the magnitude of anode current will
A) Increase if gate current is increased
B) Increase if gate current is decreased
C) Decrease if gate current is decreased
D) Not change with any variation in gate current
12) A forward voltage can be applied to an SCR after its
A) Anode current reduces to zero
B) Gate recovery time
C) Reverse recovery time
D) Anode voltage reduces to zero
A) converts constant voltage dc into ac and then into variable voltage dc
B) converts constant voltage dc into variable voltage dc directly
C) converts ac of one frequency into ac of another frequency
D) converts ac to dc
14) The terminals of a power BJT are called
A) emitter, base, collector
B) emitter, base, drain
C) source, base, drain
D) source, base, collector
15) In single phase half wave regulator, the average current over one full cycle
A) is always positive
B) may be positive or negative
C) may be negative
D) is always negative
16) The terminals of a power MOSFET are called
A) emitter, base, collector
B) source, gate, drain
C) source, base, drain
D) emitter, gate, drain
17) Thyristors are not suitable for logic circuits.
A) True
B) False
18) A semi converter operates in two quadrants.
A) True
B) False
19) A forward voltage can be applied to an SCR after its
A) Anode current reduces to zero
B) Gate recovery time
C) Reverse recovery time
D) Anode voltage reduces to zero
20) Turn on time of an SCR can be reduced by using a
A) Rectangular pulse of high amplitude and narrow width
B) Rectangular pulse of low amplitude and wide width
C) Triangular pulse
D) Trapezoidal pulse
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B
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