Electrical Circuit - MCQs Part IV

Multiple Choice Questions Topic Outline

• MCQs in AC-DC circuits
• MCQs in Resistors
• MCQs in Inductors
• MCQs in Capacitors

The Six-Parts Series

Following is the list of multiple choice questions in this brand new series:

Electrical circuits MCQs

PART 1: MCQs from Number 1 – 50                        Answer key: PART I

PART  2: MCQs from Number 51 – 100                   Answer key: PART II

PART 3: MCQs from Number 101 – 150                  Answer key: PART III

PART 4: MCQs from Number 151 – 200                  Answer key: PART IV

PART 5: MCQs from Number 201 – 250                  Answer key: PART V

PART 6: MCQs from Number 251 – 300                  Answer key: PART VI

Start with Part IV of the MCQs Series

151. Metal tin becomes superconductor at approximately

• A. 6 K
• B. 3.7 K
• C. 5 K
• D. 4.7 K

152. In a complex resistance-reactance plane, X_L is represented

• A. By an axis opposite the R axis
• B. By an axis perpendicular to the X_C axis
• C. By an axis opposite the X_C axis
• D. By an axis parallel to the R axis

153. When the net reactance in a series coil-capacitor circuit is zero at frequency f, the nature of its reactance of frequency 2f is

• A. Inductive
• B. Capacitive
• C. Resistive
• D. Infinite

154. Which of the following is a way of decreasing mutual inductance?

• A. Moving the coils closer
• B. Moving the coils apart
• C. Decreasing the number of turns of either coil
• D. Increasing the number of turns of either coil

155. The charging of a capacitor through a resistance obeys

• A. Exponential law
• B. Logarithmic law
• C. Linear law
• D. Square law

156. The Q-factor of a parallel resonant circuit is also known as

• A. Voltage magnification factor
• B. Current magnification factor
• C. Gain magnification factor
• D. Resonance magnification factor

157. What is the specific resistance of a pure silicon?

• A. 55 Ω-mm
• B. 55 Ω-m
• C. 55 Ω-cm
• D. 55 kΩ-m

158. A capacitance of 0.05 μF equals

• A. 0.05 x 10⁶ F
• B. 0.05 x 10^-6 F
• C. 0.05 x 10^-12 F
• D. 0.05 x 10¹² F

159. A 5 μF capacitor charge to 5V has a stored charge equal to

• A. 1 μc
• B. 5 μc
• C. 25 μC
• D. 200 μc

160. The factor 0.707 for converting peak to rms applies only to

• A. Square waves
• B. Triangle waves
• C. Sawtooth waves
• D. Sine waves

161. When two in-phase sine waves that have identical frequency and amplitude are added together, then the result is a sine wave with ___ the amplitude of either.

• A. Half
• B. Twice
• C. Four times
• D. One-fourth

162. Liquids that are good conductors because of ionization are called

• A. Electrolytic
• B. Bases
• C. Acid
• D. Electrolytes

163. Tungsten filament of bulbs has a hot resistance higher than its cold resistance due to its temperature coefficient which is

• A. Positive
• B. Negative
• C. Zero
• D. Infinite

164. A term used to express the amount of electrical energy stored in electrostatic field.

• A. Joules
• B. Coulombs
• C. Watts
• D. Electron-volt

165. With double the number of turns by the same length and area, the inductance is

• A. The same
• B. Doubled
• C. Quartered
• D. Quadrupled

166. The temperature coefficient of resistance of electrolytes is

• A. Negative
• B. Positive
• C. Zero
• D. Infinite

167. What refers to the lowest voltage across any insulator that can cause current flow?

• A. Conduction voltage
• B. Critical voltage
• C. Breakdown voltage
• D. Voltage capacity

168. Capacitance increase with

• A. Larger plate area and less distance between plates
• B. Larger plate area and greater distance between plates
• C. Smaller plate area and less distance between plates
• D. Higher values of applied voltage

169. What is the resonant frequency of a circuit when L of 3 microhenrys and C of 40 picofarads are in series?

• A. 14.5 kHz
• B. 145 MHz
• C. 14.5 MHz
• D. 145 kHz

170. For a triangular and sawtooth waveform the rms voltage or current equals

• A. 0.707 times peak value
• B. 0.577 times peak value
• C. 0.577 times average value
• D. 0.707 times rms value

171. If two resistances of 9 Ω and 6 Ω are connected in parallel, the total resistance is

• A. 54 Ω
• B. 0.3 Ω
• C. 15 Ω
• D. 3.6 Ω

172. Refers specifically to steady state values of quantities in ac circuits which are complex numbers.

• A. Domain
• B. Scalar quantity
• C. Vector quantity
• D. Phasor quantity

173. A capacitor is used to

• A. Block dc current
• B. Pass dc current
• C. Open voltage source
• D. Short the voltage source

174. The usual load of a dc circuit is a/an

• A. Resistor
• B. Capacitor
• C. Inductor
• D. Both inductor and capacitor

175. The second strip of an electronic resistor color-code represents

• A. The multiplier
• B. The second digit of the value
• C. The temperature
• D. The tolerance

176. Which of the following is a preferred resistor value?

• A. 520
• B. 47
• C. 43,000
• D. 54,321

177. A three-by-three, series-parallel matrix of resistors, all having the same ohmic value, would have a net resistance of

• A. One-third the value of a single resistor
• B. Three times the value of a single resistor
• C. The same value as a single resistor
• D. Nine times the value of a single resistor

178. In an ac wave, 30 degrees of phase is ___ of a cycle.

• A. ½
• B. 1/12
• C. 1/3
• D. 1/30

179. What is the value of a carbon composition resistor with the following color code: Brown, white, orange, red

• A. 190 Ω; 10 %
• B. 19 kΩ; 2 %
• C. 19 kΩ; 20 %
• D. 1.9 kΩ; 2 %

180. The electric field strength between capacitor plates has a unit of

• A. Volts per meter
• B. Volts per mil
• C. Amperes per meter
• D. Amperes per mil

181. For multi-plate capacitor, capacitance is proportional to

• A. Number of plates less one(n – 1)
• B. Number of plates plus one(n + 1)
• C. Number of plates less two(n - 2)
• D. Number of plates (n)

182. A capacitor consists of two

• A. Conductors only
• B. Dielectric only
• C. Conductors separated by a dielectric
• D. Dielectric separated by a conductor

183. How many coulombs are delivered by a storage battery in 25 hours if it is supplying current at the rate of 3 A?

• A. 2.592 x 10⁵ C
• B. 2.592 x 10³ C
• C. 2.592 x 10⁸ C
• D. 2.592 x 10¹² C

184. When frequency of an ac wave decreases, the value of X_L in a coil

• A. Approaches zero
• B. Gets larger positively
• C. Gets larger negatively
• D. Stays constant

185. The temperature-resistance coefficient of pure gold is

• A. 0.0034
• B. 0.0037
• C. 0.0038
• D. 0.0039

186. The capacitor opposes any change in voltage across it by

• A. Passing a voltage proportional to the rate of change of current
• B. Acting as a short circuit at time equal to zero
• C. Passing a current proportional to the rate of change of voltage
• D. Acting as a short circuit at time equal to infinity

187. What is the most common non-sinusoidal waveform?

• A. Square wave
• B. Triangular wave
• C. Trapezoidal wave
• D. Sawtooth wave

188. Which of the following capacitors is suitable for dc filter circuits?

• A. Mica
• B. Ceramic
• C. Paper
• D. Electrolytic

189. A series RL circuit has R of 10 Ω and X_L of 5 Ω, its impedance in rectangular form is given by

• A. 10 + j 5 Ω
• B. 10 + j 10 Ω
• C. 10 – j 5 Ω
• D. 10 – j 10 Ω

190. What is the reciprocal of capacitance?

• A. Reluctance
• B. Susceptance
• C. Elastance
• D. Conductance

191. If the output resistance of a voltage source is 4 Ω, it internal resistance should be

• A. 4 Ω
• B. 8 Ω
• C. 2 Ω
• D. Infinite

192. The curve between current and frequency is termed as

• A. Voltage curve
• B. Gain curve
• C. Power curve
• D. Resonance curve

193. What is the total effective capacitance of two 0.25 μF capacitors connected in series?

• A. 0.125 μF
• B. 1.25 μF
• C. 0.50 μF
• D. 2.5 if

194. What can be used to estimate resonant frequency and to find reactance at any frequency for any value of capacitor or inductor?

• A. Smith chart
• B. Reactance chart
• C. Impedance chart
• D. Resonance chart

195. For a parallel AC circuit, ___ is used as a reference phasor.

• A. Voltage
• B. Power
• C. Current
• D. Resistance

196. For a series AC circuit, ___ is not used as a reference phasor.

• A. Voltage
• B. Impedance
• C. Current
• D. Conductance

197. If a certain circuit has a current that is lagging the voltage by 45˚, then it displays

• A. Pure inductive reactance
• B. Resistance and capacitance reactance
• C. Resistance and inductive reactance
• D. Pure capacitive reactance

198. What maximum voltage can be applied across the capacitor for very short period of time?

• A. Working voltage
• B. Surge voltage
• C. Stray voltage
• D. Peak voltage

199. What is expected when two 20 kΩ, 1 watt resistor in parallel are use instead of one 10 kΩ, 1 watt?

• A. Provides higher current
• B. Provides less power
• C. Provides more power
• D. Provides wider tolerance

200. Which of the following materials has the lowest dielectric strength?

• A. Glass
• B. Paper
• C. Mica
• D. Teflon

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