electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
101. Thyristor can be protected from over voltages by using____________?
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A. heat sink.

B. snubber circuit.

C. voltage clamping device.

D. fuse.

102. SCR will be turned off when anode current is_______________?
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A. < latching current but greater than holding current and gate signal is 0.

B. less than holding current.

C. < latching current but greater than holding current and gate signal is present.

D. both (A) and (B).
103. Which statement is true for latching current ___________?
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A. t is related to turn off process of the device.

B. It is related to conduction process of device.

C. It is related to turn on process of the device.

D. Both C and D.

104. Which of following is not a power transistor?
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A. COOLMOS

B. IGBTs

C. SITS

D. TRIAC
105. In a three phase converter, the number of notches per cycle is____________?
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A. Nine

B. Three

C. Six

D. One

106. What is used to protect a thyristor from high di / dt conditions__________?
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A. Inductor

B. Fuse.

C. Voltage clamping device

D. Snubber circuit

107. By which one of the following we can measure the reliability of a string_____________?
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A. Factor of safety

B. String efficient

C. Reliability factor

D. Derating factor
108. In radiative coupling, the emitter radiation field_____________?
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A. Decays as R, where R is the separation distance between the emitter and the receptor

B. Decays as 1 / R, where R is the separation distance between the emitter and the receptor

C. Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor

D. Decays as 2R, where R is the separation distance between the emitter and the receptor

109. For bidirectional operation of converters____________?
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A. A series combination of controllable switch and a diode is used

B. A series combination of controllable switch and a capacitor is used

C. A parallel combination of controllable switch and capacitor is used

D. A parallel combination of controllable switch and a diode is used
110. If the anode current is 800 A, then the amount of current required to turn off the GTO is about____________?
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A. 600 A

B. 20 A

C. 400 A

D. 200 A
111. With increase in firing angle,
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A. Both harmonic distortion and quality of input current increases

B. Harmonic distortion increases and quality of input current decreases

C. Harmonic distortion decreases and quality of input current increases

D. Both harmonic distortion and quality of input current decreases

112. In rectifiers, load current flow is_________?
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A. Non directional

B. Bidirectional

C. Either (a) or (b)

D. Unidirectional
113. During gate recovery time_____________?
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A. charge carriers of J2 junction recombined

B. charge carriers of J2 junction is swept out

C. charge carrier of J1 junction removed

D. charge carriers of J3 junction is removed

114. Double edge modulation eliminates certain harmonics when the reference is a__________?
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A. Trapezoidal wave

B. Triangular wave

C. Square wave

D. Sine wave
115. Which of the following has no units?
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A. ermittivity

B. Moment of a magnet

C. Permeability

D. Magnetic susceptibility
116. Which of the following are the passive elements?
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A. Bulb

B. None of these.

C. Resistor

D. Both
117. In ac dc conversion, when the switch is closed then the sum of voltages around the loop is____________?
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A. Non zero

B. Equal to the sum of voltage when switch is open

C. Zero

D. Twice of the voltage when switch is open

118. A silicon controlled racitifier (SCR) is a ____________?
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A. Device with four junction

B. None of the above

C. Unijunction device

D. Device with three junction
119. Thermal voltage VT can be given by____________?
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A. KT/q

B. Kq/T

C. (K2/q)(T + 1/T 1)

D. qT/K

120. Between the incoming and outgoing devices in voltage commutation
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A. No overlapping operation

B. None of these

C. Small overlapping operation

D. Large overlapping takes place

121. A modern power semiconductor device that combines the characteristic of BJT and MOSFET is_____________?
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A. MCT

B. FCT

C. IGBT

D. GTO

122. When a large surge current of very short duration flows through a thyristor then which one of the following device will operate to protect the thyristor ___________?
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A. Fast acting current limiting device (FACL fuse)

B. CB

C. Snubber circuit

D. Voltage clamping device

123. During reverse recovery time__________________?
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A. charge carrier of junction J2 recombined

B. charge carrier of junction J1 is swept out

C. charge carrier of junction J3 is swept out

D. both B and C
124. The reverse recovery time of diode is trr = 3 Is and the rate off all of the diode current is di/dt = 30 A/Is. The storage charge current QRR is___________?
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A. 140 Is

B. 135 Is

C. 130 Is

D. 145 Is

125. In commutation PAC stands for_______?
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A. Phase angle converter

B. Phase and commutation

C. Phase angle commutation

D. Permanent angle converter

126. An ideal switch is___________?
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A. All of these

B. Carry current in any direction when it is on

C. Lossless

D. Does not carry any current in any direction when it is off

127. An SCR is made up of silicon because?
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A. silicon has large leakage voltage than germanium

B. silicon has small leakage current than germanium

C. silicon has large leakage current than germanium

D. silicon has small leakage voltage than germanium

128. In a 3 phase VSI out of eight valid states, the number of valid states that produce zero ac line voltages is/are_________?
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A. Four

B. two

C. One

D. Three

129. Electrical power output in a d.c. generator is equal to____________?
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A. Mechanical power input iron and friction losses copper losses

B. Electrical power developed in armature copper losses

C. Electrical power developed in armature iron and copper losses

D. Mechanical power input iron and friction losses

130. Power transistor are type of___________?
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A. IGBTs

B. B.JTs

C. MOSFETs

D. All of above
131. Spread time is defined as the interval during which_____________?
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A. anode voltage drops from 10 % of its initial value to zero

B. anode current rises from 90 % to its final value

C. both (A) and (B)

D. anode current rises from 10 % to 90 % of its final value

132. The on state voltage drop of IGBT consists of__________?
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A. All of these

B. Drop across MOSFET portion

C. Drop across the drift region

D. Drop across the collector junction

133. Single phase VSI are mainly used in___________?
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A. All of these

B. Ups

C. Power supplies

D. Multilevel configuration

134. What happen due to high di / dt____________?
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A. None of these

B. Breakdown of junction

C. Insulation failure

D. Local hot spot
135. LISN is a device used to measure conducted emissions. LISN stands for_____________?
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A. Line integrated stored network

B. Line integrated stabilization network

C. Line impedance stabilization network

D. Laser integrated stabilization networking

136. For an SCR gate aEUR" cathode characteristic is a straight line of 130. For triggered source volume of 15 V and allowable gate power dissipation of 0.5 W compute the gate source resistance_____?
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A. 11.19 I.

B. 108 I.

C. 111.9 I.

D. 115 I

137. Which one is most suitable power device for high frequency (>100 KHz) switching application?
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A. Power MOSFET

B. Schottky diode

C. Microwave transistor

D. BJT

138. Practical way of obtaining static voltage equalization in series connected SCRs is by the use of____________?
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A. Resistors of the same value across each SCR

B. One resistor in series with each SCR

C. One resistor across the string

D. Resistors of different values across each SCR

139. The capacitance of reversed bised junction J2 in a thyristor is CJ2 = 20 pF and can be assumed to be independant of the off state voltage. The limiting value of the charging current to turn on the thyristor is 16 mA. What is the critical value of dv/dt?
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A. 800 V/s

B. 600 V/s

C. 1200 V/s

D. 1000 V/s

140. Magnetic flux has the unit of
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A. Weber

B. Ampere-turn

C. Tesla

D. Newton

141. A single phase one pulse controlled circuit has a resistance R and counter emf E load 400 sin(314 t) as the source voltage. For a load counter emf of 200 V, the range of firing angle control is _____?
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A. 60 to 120.

B. 60 to 180.

C. 30 to 150.

D. 30 to 180.

142. Dynamic equalising circuit is useful____________?
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A. To limit di / dt of SCR

B. To limit dV / dt of SCR

C. For voltage equalisation

D. Both B and C
143. The man made noise sources is / are_____________?
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A. Switches, radio interferences

B. All of these

C. Computers, digital electronics

D. Motors

144. Choppers is a_______________?
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A. DC AC converters

B. DC DC converters

C. AC AC converters

D. AC DC converters

145. A Triac has three terminals viz ___________?
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A. Two main terminal and a gate terminal

B. None of the above

C. Cathode, anode, gate

D. Drain, source, gate

146. COOLMOS device can be used in application up to power range of___________?
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A. 500 VA

B. 2 KVA

C. 1 KVA

D. 100 KVA

147. Unipolar modulation is generally used in____________?
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A. AC AC converters

B. DC AC converters

C. DC DC converters

D. AC DC converters

148. Inductor does not allow the sudden change of
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A. None of the above

B. voltage

C. power

D. current
149. ON state voltage drop across SCR lie between the range_____________?
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A. 0 0.5 V.

B. 0.5 1 V.

C. 1.5 2 V.

D. 1 1.5 V.
150. Let of a thyristor Vc1, Vc2, Vc3 are forward break over voltage for gate current Ig1, Ig2, Ig3 respectively. Then________________?
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A. Vc1 > Vc2 > Vc3 when Ig1 > Ig2 > Ig3.

B. Vc1 > Vc2 > Vc3 when Ig1 < Ig2 < Ig3.

C. Vc1 = Vc2 = Vc3 any value of Ig.

D. Vc1 > Vc2 > Vc3 when Ig1 aYEN Ig2 &Atil