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
151. In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output
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A. Switches between 1 / 2 and + 1 / 2

B. Zero

C. Switches between 0 and + 1

D. Switches between 1 and + 1

152. The conduction losses in IGBT is____________?
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A. Equal to that of MOSFET

B. Equal to that of BJT

C. More than that of MOSFET

D. Lower than that of MOSFET
153. DIAC are specifically designed to trigger______________?
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A. SCR

B. Only (a) and (b)

C. GTO

D. TRIAC

154. Example of a voltage clamping device______________?
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A. metal oxide varistor

B. snubber circuit

C. fast acting fuse

D. aluminium block

155. Which following is a two terminal three layer device?
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A. BJT

B. None of above

C. Power dioed

D. MOSFET

156. In a silicon controlled rectifier, the load is connected___________?
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A. In series with cathode

B. In series with anode

C. Across cathode

D. Across anode

157. In BJT, switching losses occurs___________?
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A. Only at turn on

B. Only at turn off

C. Both at turn on and off

D. None of these

158. The maximum di/dt in a SCR is____________?
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A. Directly proportional to supply voltage

B. Directly proportional to inductance in the circuit

C. Inversely proportional to supply voltage

D. Both A and B
159. The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are____________?
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A. Directly proportional to their harmonic order

B. None of these

C. Inversely proportional to their harmonic order

D. Not related to their harmonic order

160. A thyristor equivalent of a thyratron tube is a _________?
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A. Silicon controlled-rectifier SCR

B. None of above

C. Diac

D. Triac

161. A GTO can be turned on by applying___________?
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A. Positive drain signal

B. Positive source signal

C. Positive gate signal

D. None of these

162. In the operation and control of both naturally commutated and forced commutated SCR base converter, commutation plays an important role. The converters is / are ___________?
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A. DC DC

B. All of these

C. DC AC

D. AC DC

163. Which of the following is disadvantage of fast recovery diodes?
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A. Recovery is only 50 s

B. Recovery is only 5 s

C. Doping is carried out

D. None of these

164. For a buck converter to reduce the conduction losses in diode
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A. A low on resistance switch can be added in parallel

B. A high on resistance switch can be added in parallel

C. A low on resistance switch can be added in series

D. A high on resistance switch can be added in series

165. Due to non sinusoidal waveform of the input current, the power factor of the rectifier is____________?
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A. Negatively affected by firing angle

B. Negatively affected by distortion of the input current

C. Positively affected by both firing angle and distortion of the input current

D. Both (a) and (b)
166. In a single phase full wave rectifier, during blocking state the pea inverse voltage of diode is______________?
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A. 2 V m

B. 4 V m

C. V m

D. V m / 2

167. The function of snubber circuit connected across the SCR is to___________?
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A. Decrease di / dt.

B. Suppress dV / dt.

C. Increase dV / dt.

D. Decrease dV / dt.

168. Compared to transistor, _________ have lower on state conduction losses and higher power handling capability?
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A. Semi conductor diodes

B. Thyristor

C. MOSFETs

D. TRIACs

169. Why resistor is used in Snubber circuit_________________ ?
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A. To minimize the discharging current

B. To minimize the charging current

C. All of these

D. To minimize the loss

170. In current commutated DC-DC choppers, the voltage spike appears across the load when_____________?
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A. Voltage across the commutating inductances collapses

B. The capacitance voltage adds to the supply voltage

C. Both A. and B.

D. None of these

171. The switching function of semiconductor devices can be characterized with___________?
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A. Duty ratio, frequency and time delay

B. Frequency only

C. Duty ratio and frequency

D. Duty ratio only

172. IGBT stands for___________?
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A. Insulated gate bidirectional transistor

B. Inductive gate bipolar transistor

C. Inductive gate bidirectional transistor

D. Insulated gate bipolar transistor
173. Which of the following is used in heat sink_____________?
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A. Carbon

B. Iron

C. Aluminium

D. ilver

174. Which quantity consists of a unit 1KWh ?
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A. Charge

B. Energy

C. Time

D. Power

175. An SCR is considered to be a semi controlled device because_______?
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A. it can be turned ON only during one half cycle of an AC.

B. it conducts only during one half cycle of an alternating current wave.

C. it can be turned ON but not OFF with a gate pulse.

D. it can be turned OFF but not ON with a gate pulse.

176. Anode current in an SCR consists of____________?
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A. holes only

B. electrons only

C. either electron or holes

D. Both electron and holes

177. A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be_____________?
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A. 4, 6

B. 6, 4

C. 5, 7

D. 7, 5
178. A rectifier with an external low pass filter is an example of______________?
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A. Embedded converters

B. Indirect switch matrix circuits

C. All of these

D. Direct switch matrix circuits
179. A thyristor is basically________?
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A. A set of SCRs

B. PNPN device

C. A set if SCR,diac and triac

D. A combination of diac and triac

180. Internal resistance of ideal voltage source is ?
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A. finite

B. zero

C. 100 ohms

D. infinite

181. The output power of the cascaded amplifier / attenuator system can be determined using___________?
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A. Gain in dB of amplifier and attenuator

B. Actual gain of attenuator

C. Actual gain of amplifier

D. Actual gain of amplifier and attenuator
182. Thyristor can be protected from over voltages by using
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A. 10 mA.

B. 60 mA.

C. 40 mA.

D. 23 mA.

183. The resistivity of the conductor depends on
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A. length of the conductor.

B. area of the conductor.

C. type of material.

D. none of these.

184. If holding current of a thyristor is 2 mA then latching current should be_____?
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A. 0.009 A.

B. 0.01 A.

C. 0.002 A.

D. 0.004 A.
185. Number of PN junction in an SCR is____________?
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A. Four

B. Five

C. Three

D. Two

186. The most suited gate pulses given to the AC regulator with R L load can be in the form of____________?
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A. A train of pulses

B. Continuous signal

C. Large isolating pulse transformer

D. None of these

187. BCT is used for____________?
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A. Low power phase control

B. Low power current control

C. High power current control

D. High power phase control
188. The output current in PWM DC DC converters is equal to___________?
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A. Product of an average inductor current and a function of duty ratio

B. Either A. or B.

C. Average value of the output inductor current

D. None of these

189. In constant frequency PWM, at perturbation the amplitude of the sinusoidal component is a___________?
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A. None of these

B. Linear function

C. Constant function

D. Non linear function

190. Voltage dependent resistors are usually made from________________?
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A. Silicon Carbide

B. Nichrome

C. Graphite

D. Charcoal

191. When electric current passes through a bucket full of water, lot of bubbling is observeD. This suggests that the type of supply is____________?
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A. none of the above

B. D. C.

C. A. C.

D. any of above two

192. No-load on a transformer is carried out to determine______________?
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A. magnetising current and loss

B. copper loss

C. efficiency of the transformer

D. magnetising current

193. The condition for the validity under Ohms law is that_______________?
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A. current should be proportional to the size of the resistance

B. resistance must be wire wound type

C. resistance must be uniform

D. temperature at positive end should be more than the temperature at negative end

194. All good conductors have high____________?
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A. thermal conductivity

B. reluctance

C. conductance

D. resistance

195. The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative w.r.t cathode are known as_____________________?
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A. both as forward characteristics

B. both as reverse characteristics

C. former as forward characteristics and later as reverse characteristics

D. former as reverse characteristics and later as forward characteristics

196. A rheostat differs from potentiometer in the respect that it_____________?
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A. has lower wattage rating

B. has higher wattage rating

C. has large number of turns

D. offers large number of tapping

197. It becomes more difficult to remove_________________?
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A. third electron from the orbit

B. any electron from the orbit

C. first electron from the orbit

D. second electron from the orbit

198. The Graetz bridge makes excellent use of ______________?
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A. Potential transformer

B. Power transformer

C. Current transformer

D. SCR

199. Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as________?
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A. 5:02

B. 25:04:00

C. 2 : 5

D. 4:25

200. The filament of an electric bulb is made of______________?
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A. tungsten

B. aluminium

C. carbon

D. nickel