186. REE Board Exam September 2003
The following are in series R = 1,000 Ω, L = .100 μH and C = 20,000 pF. The voltage across the circuit is 100 V, 60 kHz. What is the total impedance expressed in ohms?
A. 1882 ohms C. 2132 ohms
B. 1000 ohms D. 1885 ohms
187. REE Board Exam October 2000
A series circuit has an applied voltage of v = 220 sin (ωt + 30°) and draws a current of i = 10 sin (ωt - 30°). What is the average power and power factor of the circuit?
A. 1,905 W, 86.6% lagging C. 2,200 W, 100%
B. 1,905 W, 86.6% lagging D. 1,100 W, 50% lagging
188. REE Board Exam September 2001
A coil has an impedance of 75.4 Ω when connected a across a source of 60 Hz. The same coil yields an impedance of 54.8 Ω when connected across a source having a different frequency of 30 Hz. What is the coil’s inductance?
A. 245.7 mH C. 158.6 mH
B. 512.8 mH D. 341.7 mH
189. REE Board Exam April 1996
A circuit consists of a 4 ohms resistor and a 300 μF capacitor in series. It is connected across a 60 Hz voltage source with a 500 V peak voltage.
What is the phasor form of the current?
A. 𝐼 = 19.57∠57.5° A C. 𝑰 = 𝟑𝟔. 𝟓∠𝟔𝟓. 𝟕° A
B. 𝐼 = 8.84∠73.2° A D. 𝐼 = 10.5∠65.7°
A
190. REE Board Exam September 2000
Find the power in a circuit if i(t) = 10 sin (ωt - 30) and v(t) = 220 sin (ωt + 30).
A. 550 watts C. 1900 watts
B. 2200 watts D. 1500 watts
191. REE Board Exam April 1997
A current of 2.5 A flows through a series circuit consisting of a 100 Ω resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance?
A. XC = 91.86 Ω C. XC = 154.45 Ω B. XC = 39.19 Ω D. XC = 184.0 Ω 192. REE Board Exam April 1995
In a series RC circuit the voltage across the capacitor and the resistor are 60 volts and 80 volts respectively. The total voltage is
A. 70 C. 140
B. none of these D. 100 193. EE Board Exam October 1984
An industrial coil has a resistance of 32 ohms and reactance of 24 ohms and rated 440 volts at 60 Hz.
A factory will connect the coil to a 440 V, 50 Hz supply. Solve for the value of a series resistor needed to avoid over-current condition.
A. 2.07 ohms C. 2.44 ohms
B. 2.64 ohms D. 2.25 ohms
194. REE Board Exam October 1998
Two relays each with 20 ohms resistance and 0.16 H inductance are connected in series. What is the equivalent impedance?
A. 20 + j102.2 Ω C. 40 + j120.63 Ω B. 20 + j95.32 Ω D. 40 + j25.32 Ω
195. EE Board Exam October 1990
An inductive coil takes a current of 2 A and consumes 160 W when connected to a 240 V ac supply. A second coil when connected across the same supply takes 3 A and 500 W. Find the total power when the two coils are connected in series to this supply,
A. 144.56 W C. 150.22 W
B. 134.31 W D. 128.35 W
196. EE Board Exam October 1985
A coil draws 1875 watts when connected to a 150 V dc source. It consumes 30.72 watts when use on a 240 V, 60 Hz ac source. Find the inductance of the coil.
A. 0.0255 H C. 0.0153 H
B. 0.0341 H D. 0.0240 H
197. REE Board Exam October 1994
A current of 10 A and a power factor of 0.8 lagging is taken form a single phase 250 volt supply. The reactive power of the system is
A. 1500 vars C. 2500 vars
B. 2000 vars D. none of these 198. REE Board Exam October 1996
The resistor of 6 Ω and unknown impedance coil in series draws 12 A from a 120 V, 60 Hz line. If the real power taken from the line is 1152 watts, what is the coil inductance?
A. 15.9 mH C. 20 mH
B. 10 mH D. 1.59 mH
199. REE Board Exam April 1997
Determine the power factor angle in the series circuit which consists of R = 25 Ω, L = 0.2 H, across a power supply of 200 V, 30 Hz.
A. 36.4° C. 52.4°
B. 46.4° D. 56.4°
200. EE Board Exam April 1993
The impedance coils absorbs 250 watts when
201. REE Board Exam September 2001
In laboratory experiment, the impedance of the coil was obtained at 60 Hz and 30 Hz. These are 75.48 ohms and 57.44 ohms respectively. What is the inductance of the coil?
A. 150 mH C. 42.5 mH
B. 182.5 mH D. 2.1 mH
202. REE Board Exam September 2002
A 10 ohms inductive resistor is connected in series with an unknown capacitance. At 60 Hz the
impedance of the circuit is 10 + j11.72 ohms. At 30 Hz the impedance of the circuit is 10 – j5 ohms.
What is the value of L in millihenrys?
A. 50 C. 100
B. 500 D. 250
203. REE Board Exam April 1995
An impedance coil takes 10 A and absorbs 250 W when connected across a 220 V, 60 Hz source. What power will it absorb when connected across 110 V, 25 Hz mains?
A. 539 W C. 439 W
B. 239 W D. 339 W
204. EE Board Exam October 1984
An industrial coil has a resistance of 32 ohms and a reactance of 24 ohms and rated 440 volts at 60 Hz.
A factory will connect the coil to a 440 V, 50 Hz supply. How much percentage over-current will the coil suffer?
A. 5% C. 6%
B. 10% D. 8%
205. REE Board Exam March 1998
A 25 Ω resistor connected in series with a coil of 50 Ω resistance and 150 mH inductance. What is the power factor of the circuit?
A. 85% C. 90%
B. 80% D. 75%
206. REE Board Exam April 1997
A current of 2.5 A flows through a series circuit consisting of a 100 ohm resistor and an unknown capacitor across a source of 460 V, 50 Hz. What is the value of the capacitive reactance?
A. XC = 91.86 Ω C. XC = 154.45 Ω B. XC = 39.19 Ω D. XC = 184 Ω
207. REE Board Exam October 1998
The ohmic resistance of a large magnetic contactor is measured to be 20 ohms. A 230 V is impressed on the contractor and the current is taken as 3.2 A. Neglecting core loss, determine the inductance of the contractor in mH?
A. 261 C. 183
B. 315 D. 251
208. REE Board Exam March 1998
A load of 20 + j35 Ω is connected across a 220 V source. Determine the power factor and the VARS.
A. 49.6%, 1042 vars C. 85.3%, 975 vars
B. 52.2%, 1023 vars D. 42.3%, 1087 vars
209. EE Board Exam October 1990
Find the total impedance in rectangular form for the following three series impedances:
12∠10° ohm, 25∠15° ohm, 34∠26° ohm.
A. 66.52 + j23.46 Ω C. 74.31 + j21.56 Ω
B. 68.34 + j20.54 Ω D. 67.70 + j22.04 Ω
210. REE Board Exam October 1997
An impedance draws a current i = 10 cos (ωt – 30°) A from a voltage, v = 220 sin (ωt + 30°) V. What is the impedance?
A. 15.6 – j15.6 Ω C. 19.1 – j11.1 Ω B. 15.6 + j15.6 Ω D. 11.0 + j19.1 Ω 211. EE Board Exam April 1990
A series resistance-capacitance (R-C) circuit is connected to a 230 volt 60 cycle source. If the power taken by the circuit is 4,800 watts and the voltage drop across the resistor is 115 volts, calculate the capacitance of the capacitor.
A. 540 μF C. 556 μF
B. 530 μF D. 503 μF
212. REE Board Exam March 1998
A 50 μF and 100 μF capacitors are connected in series and across a 100 sin (ωt + 30°) voltage. Write the equation of the current.
A. 1.26 sin (ωt + 120°) A C. 5.65 sin (ωt + 120°) A
B. 1.26 sin (ωt + 90°) A D. 5.56 sin (ωt + 90°) A
213. EE Board Exam April 1993
A 100∠0° V, 120 Hz generator and a 80∠0° V, 60 Hz generator are connected in series with a 60 V battery and a coil. The resistance and inductance of the coil are 3 and 2.65 mH, respectively. Determine the rms current of the coil.
A. 42.54 A C. 43.55 A
B. 44.24 A D. 40.44 A
214. REE Board Exam October 1996
A series circuit composed of 100-ohm resistor and a 20-microfarad capacitor connected across a 240-V, 60 Hz line. Which of the following answers is WRONG?
A. the impedance of the circuit is 167 ohms B. angle between the current and the voltage
vectors is 53.1 degrees
C. the resulting current is 0.723 ampere
D. the voltage across the resistance is 144.6 volts 215. REE Board Exam April 1994
A capacitance is connected to a 115-V, 25 Hz mains and takes 5 A. What current will it take when the capacitance and the frequency are both doubled?
A. 2.5 A C. 20 A
B. 5 A D. 10 A
216. REE Board Exam October 1996
A capacitor is rated 100 kVAR, 380 V, 50 Hz, What will its rating be at 60 Hz, 220 V?
A. 50 kVAR C. 90.9 kVAR
B. 40 kVAR D. 57.7 kVAR
217. REE Board Exam October 1992
A resistor and a capacitor are connected in series across a supply of 250 V. When the supply frequency is 50 Hz the current in the circuit is 5 A. When the supply frequency is 60 Hz, the current is 5.8 A. Find the value of the capacitance.
A. 58.3 μF C. 60.2 μF
B. 69.1 μF D. 70.2 μF
218. EE Board Exam October 1993
A series circuit composed of a 0.2 Henry inductor and a 74-microfarad capacitor is connected to a 60 V variable frequency source. At what frequency is the current be 4 amperes with a lagging power factor?
A. 50 Hz C. 48 Hz
B. 51 Hz D. 49 Hz
219. REE Board Exam October 1998
The maximum instantaneous voltage and current output of an alternator are 300 V and 20 A, respectively. What is the power output in watts if the voltage leads the current by 30°?
A. 2598 C. 5196
B. 3000 D. 6000
220. REE Board Exam October 1998
A 50-microfarad is connected in series with a coil having 50 ohms resistance and 150 mH inductance.
The source voltage is 100 sin (ωt – 120°) V. What is the maximum power?
A. 199 watts C. 212 watts
B. 147 watts D. 165 watts
221. REE Board Exam October 1997
An impedance draws a current i = 10 cos (ωt – 30°) A from a voltage v = 220 sin ωt. What is the maximum power?
A. 2200 watts C. 190.5 watts B. 1100 watts D. 1320 watts
222. REE Board Exam April 1995
An incandescent lamp load generally
considered to be made up of resistors take 4.8 kW from a 120 V ac source. The instantaneous maximum value of power is
A. 4800 W C. 480 W
B. 2400 W D. 9600 W
223. ECE Board Exam November 1998
The term used for an out-of-phase, non-productive power associated with inductors and capacitors?
A. peak envelope power C. true power B. effective power D. reactive power 224. ECE Board Exam November 2001
What is the capacitive reactance of a 33 microfarad capacitor at 6500 Hz?
A. 7.4 0hms C. 0.74 ohms
B. 96 0hms D. 1122 ohms 225. ECE Board Exam November 1999
The power dissipated across the resistance in an AC circuit.
A. true power C. reactive power B. real power D. apparent power 226. ECE Board Exam April 2000
What is the capacitive reactance of a 33 microfarad capacitor at 500 Hz?
A. 1,000,000 ohms C. 0 ohms
B. 144 ohms D. 9.55 ohms
227. ECE Board Exam November 1998
What is the reactance of a 25 mH coil at 600 Hz?
A. 0.011 ohm C. 785 ohms
B. 94,000 ohms D. 94 ohms
228. ECE Board Exam April 1999
Ignoring capacitance effects, what is the impedance of a 250 mH coil with an internal resistance of 55 ohms at 60 Hz?
A. 149.2 ohms C. 94.2 ohms
B. 109 ohms D. 10,900 ohms
229. ECE Board Exam November 1999
Ignoring any inductive effects, what is the impedance of RC series capacitor made up of a 56 kilo ohms resistor and a 0.033 μF capacitor at a signal frequency of 450 Hz?
A. 66,730 C. 10,730
B. 57,019 D. 45,270
230. ECE Board Exam April 2000
Assuming an ideal capacitor, with no leakage, what is the capacitive reactance of 10 microfarad capacitance of DC (0 Hz)?
A. 0 ohms B. 16000 ohms C. 1,000,000 ohms
D. infinite capacitive reactance 231. ECE Board Exam April 1998
The impedance in the study of electronics is represented by resistance and _____
A. Reactance B. Capacitance C. Inductance
D. Inductance and capacitance 232. ECE Board Exam November 2000
One of the following satisfies the condition of Ohm’s Law
A. Application to metals which heated up due to flow of current over them
B. Application to AC circuit having its impedance used in place of resistance
C. Application to semiconductor D. Application to vacuum radio valves
233. The effective voltage across a circuit element is (20 + j10) and the effective current through the element
is 4 – j3 A. Calculate the true and reactive power taken by the element.
A. 50 watts & 100 vars lagging B. 50 watts & 100 vars leading C. 110 watts & 20 vars lagging D. 110 watts & 20 vars leading
234. The voltage across a given circuit is 75 + j50 V. What is the power supplied to the circuit if the current through it is (8 – j5) A?
A. 850 W C. 750 W
B. 550 W D. 350 W
235. Find average power in a resistance R = 10 ohms if the current in series form is i = 10 sin ωt + 5 sin 3ωt voltage and resulting current?
A. e = 398.4 sin 60t and i = 21.6 sin 60t B. e = 325.5 sin 377t and i = 21.6 sin 377t C. e = 230 sin 377t and i = 15.3 sin 377t D. e = 230 sin 120t and i = 15.3 sin 120t
237. A resistor R and a capacitor C are connected in series across a 100 V, 60 cycle source. The reading of an ammeter connected in the circuit is 2 A and the reading of a voltmeter connected across the capacitor is 80 V. Calculate the values of R and C.
A. 66 Ω & 30 μF C. 30 Ω & 66 μF B. 30 Ω & 60 μF D. 36 Ω & 60 μF 238. A series circuit consisting of a 66.2 μF capacitor and
a variable resistor. For what two values of resistance will the power taken by the circuit be 172.8 watts, if the impressed 60-cycle emf is 120 volts?
A. 85.33 & 3.33 ohms C. 5.33 & 3.0 ohms
B. 53.33 & 30 ohms D. 83.33 & 5.33 ohms
239. A series circuit composed of 0.2 H inductor and a 74 μF capacitor is connected to a 60 V variable frequency source. At what frequency will the current be 4 A with lagging power factor?
A. 47.767 Hz C. 60 Hz
B. 74.68 Hz D. 50 Hz
240. A 30 ohm resistor is connected in parallel with an inductor of inductive reactance XL. The combination is then connected in series with a capacitor of reactance XC. What is the value of XL and XC if the total impedance is 1.92 ohms?
A. 7.84 and 7.34 C. 44.8 and 84.21 B. 47.4 and 47.3 D. 84.7 and 34.7 241. An impedance of 100 Ω resistance and an unknown
inductance is connected across the capacitor. The resulting impedance is a pure resistance of 500 Ω if
ω = 105 rad/sec. Calculate the values of inductor and respectively. What is the voltage across this circuit?
A. 160 V C. 100 V
B. 140 V D. 50 V
243. The open circuit voltage of an alternator is 127 V and its internal impedance is 10∠10° Ω. Find the voltage across a load of 30∠ − 30° Ω.
A. 𝟏𝟎𝟎∠ − 𝟗. 𝟕° V C. 79∠ − 10° V B. 97∠ − 10° V D. 100∠ − 7.9° V 244. The maximum values of alternating voltage and
current are 400 V and 20 A, respectively. In a circuit connected to 50 Hz supply and these quantities are sinusoidal. The instantaneous values of voltage and current are 283 V and 10 A respectively at t = 0 both same coil when carries an alternating current of 9 A at 25 Hz, the potential difference is 24 V. Find the power when it is supplied by 50 V, 50 Hz supply.
A. 45 W C. 63 W
B. 54 W D. 30 W
246. Two coils A and B are connected in series across a 240 V, 50 Hz supply. The resistance of A is 5 Ω and the inductance of B is 0.015 H. If the input from the supply is 3 kW and 2 kVAR, find the inductance of A and resistance of B.
A. 0.0132 H & 8.3 Ω C. 0.026 H & 12 Ω B. 0.215 H & 3.8 Ω D. 0.031 H & 5.3 Ω 247. A current of 5 A flows through a non-inductive resistance in series with a choking coil when supplied at 250 V, 50 Hz. If the voltage across the resistance is 120 V and across the coil is 200 V, calculate the power absorbed by the coil in watts.
A. 168.75 W C. 51.37 W
B. 137.5 W D. 75.31 W
248. A single phase, 7.46 kW motor is supplied from a 400 V, 50 Hz AC mains. If its efficiency is 85% and the power factor is 0.8 lagging, find the reactive component of the input current.
A. 16.46 A C. 27.43 A
B. 21.95 A D. 21 A
249. A series RLC circuit consists of 20 ohms resistance, 0.2 H inductance and an unknown capacitance.
What is the value of the capacitance if the circuit has a leading angle of 45° at 60 Hz?
A. 35.18 μF C. 27.8 μF
B. 47.9 μF D. 30.7 μF
250. A 3 HP, 120 V, 60 Hz induction motor operating at 80% efficiency and 0.866 lagging power factor is to be used temporarily with 240 V, 60 Hz source. What resistance in series with the motor will be required for the motor to have 120 V across its terminals at full load?
252. A resistor and a coil are connected in series with a voltage source. If the voltage across the coil is 10 sin (866t + 70°) V and the current flowing through the resistor is 2 cos (866t – 80°) A, what is the resistance of the coil?
A. 4.92 Ω C. 5 Ω
B. 2.5 Ω D. 4.33 Ω
253. A coil has a resistance of 6 ohms and an inductance of 0.02 H. When a non-inductive resistor is connected in series with the coil, the current drawn when connected to 220 V DC source is equal to the current drawn by the coil alone across a 220 V, 60 Hz source. Determine the resistance of the non-inductive resistor.
A. 3.63 Ω C. 3.69 Ω
B. 6.39 Ω D. 3.96 Ω
254. A series RL circuit has L = 0.02 H and an impedance of 17.85 Ω. When a sinusoidal voltage is applied, the current lags the voltage by 63.5°. What is the value of the angular frequency?
A. 400 rad/sec C. 600 rad/sec B. 500 rad/sec D. 800 rad/sec 255. A 50 resistance is connected in series with a coil
having 25 resistance and 150 mH inductance. The circuit is connected to a voltage source of 200 sin t.
Calculate the instantaneous current.
A. 2.9 sin t C. 2.1 sin (t – 37) B. 1.7 sin (t + 37) D. 5.11 sin (t - 37)
256. A coil having a resistance of 25 and an inductance of 150 mH is connected in series with a 80 F capacitor across a voltage source of 200 sin 377t.
What is its instantaneous current?
A. 5.84 cos (377t - 43) C. 5.84 sin (377t + 43)
B. 5.84 sin 377t D. 5.84 sin (377t - 43)
257. A coil with a 15 resistance is connected in series with a capacitor. At 60 Hz source, the impedance is measured at 15 + j11.27 while in 30 Hz source it is
measured as 15 – j7.24 . Calculate the inductance of the coil.
A. 52.7 mH C. 41.2 mH
B. 65.8 mH D. 11.27 mH
258. An impedance coil has a resistance and inductance of 20 ohms and 0.05 H respectively. What value of dc voltage can be applied to the coil in order that it will take the same power from a 220 V 60 Hz mains?
A. 188 V C. 160 V
B. 220 V D. 120 V
259. A ½ HP, 110 V, 60 Hz, single-phase induction motor has an efficiency of 88% and a power factor of 0.707 lagging at rated load. This motor is to be connected temporarily on a 220 V, 60 Hz line. Determine the resistance are connected in series across a 110 V, 60 cycle line. The current and power delivered by the source are respectively 4.1 A and 300 W. If the voltage across coil A is twice that across coil B, calculate the inductance of coil B.
A. 8.63 mH C. 9.02 mH
B. 7.36 mH D. 4.49 mH
261. The total voltage in a series RL circuit ____ the current by an angle ____.
A. lags, of 90
B. lags, between 0 and 90
C. leads, between 0 and 90
D. leads, between 90 and 180
262. In a series RL circuit, the inductor current ____ the resistor current.
A. lags C. leads
B. is equal D. is negative 263. The impedance triangle is similar to the ____ triangle
with the resistance phasor in place of the ____
A. current, resistor current B. current, resistor voltage C. voltage, impedance D. voltage, resistor voltage
264. In the impedance triangle the inductive reactance and impedance phasor are analogous to the ____
and ____ phasor respectively in the voltage triangle.
A. inductive voltage, total voltage B. inductive current, total current C. inductive voltage, resistive current D. inductive current, resistive current
265. In a series RL circuit, phasor diagram, total voltage may be represented by the ____ phasor and the resistor voltage may be represented by the ____
voltage.
A. current, voltage
B. impedance, resistance C. current, resistance D. impedance, inductance
266. The phase angle of a series RL circuit is the angle between the ____ phasor and the ____ phasor.
A. resistance, inductive reactance B. resistance, impedance
C. inductive reactance, impedance D. none of the above
267. The phase angle of a series RL circuit may be computed ____ as ____ or ____.
A. cos-1 R/XL, sin-1 XL/R, tan-1 R/Z B. cos-1 R/Z, sin-1 XL/R, tan-1 R/XL
C. cos-1 Z/XL, sin-1 R/Z, tan-1 XL/R D. cos-1 R/Z, sin-1 XL/Z, tan-1 XL/R
268. In the circuit of figure shown the effective value of the resistor voltage is ____ volts.
5 Ω
Eeff. = 10 V 5 Ω
A. 𝟓√𝟐 C. 5/√2
B. 5 D. 10
269. A(n) ____ stores and returns energy to a circuit while a(n) ____ dissipates energy.
A. resistor, impedance C. inductor, resistor
B. resistor, inductor D. inductor, reactance
270. For an RL circuit, the power factor cannot be less than ____ or greater than ____.
A. 0, 1 C. 0, -1
B. 1, 0 D. –1, 0
271. The voltage across a capacitor ____ the current through it by ____.
A. lags, 45 C. leads, 0
B. lags, 90 D. leads, 90
272. If the resistance in a series RC circuit is increased the magnitude of the phase angle
A. increases B. remains the same C. decreases
D. changes to an indeterminate manner
273. In a series RC circuit, the current ____ the total voltage by an angle.
A. lags, of 45
B. lags of 0
C. leads, between 0 and 90
D. leads, of 90
274. The resistance phasor for a series RC circuit points to the right. The capacitive reactance phasor points
____ while the diagonal of the rectangle having there two phasors as sides represents the ____.
A. up, impedance C. down, impedance
B. left, current D. up, total voltage 275. The phase angle for a series RC circuit is defined as the angle between the ____ and the ____ phasors.
A. current, resistance voltage B. current, total voltage
C. resistance voltage, capacitor voltage D. R, XC
276. The phase angle for a series RC circuit may be computed as the angle between the ____ and the ____ phasors.
A. resistance, impedance B. resistance, reactance C. resistance, impedance D. none of the above
277. If a series RC circuit with 10 ohms and XC = 10 ohms carries a current of 1 ampere effective value the resistor voltage is ____ volts effective and the capacitor voltage is ____ volts effective.
A. 10/√2, 10/√2 C. 10√2, 10√2
B. 10, 10 D. 5, 10
278. The power dissipated in a series RL circuit with R
=10 ohms and XC = 10 ohms carrying an effective current of 3 amps is ____ watts.
A. 30 C. 90
B. 30√2 D. 90√2
279. The magnitude of the power factor of an RC circuit with R = 10 ohms, XC = 10 ohms. I = 2 amp effective
281. The net reactance in an RLC circuit is
A. XL C. XC
B. XC – XL D. XL - XC
282. The impedance of a series RLC circuit is ____.
A. √R2+ XL2+ XC2 C. respectively. The input voltage should be
A. 70∠45° V C. 105∠ − 42° V
B. 𝟏𝟎𝟎∠ − 𝟑𝟕° V D. 108∠ − 60° V 284. The transient current are due to
A. voltage applied to circuit B. resistance of the circuit C. impedance of the circuit
D. changes in stored energy in inductance and capacitance
285. To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will
A. increase B. decrease
C. remain nearly the same D. become indeterminant
286. In a series R-L circuit. VL ____ VR by ____ degrees.
A. lags, 45 C. leads, 90
B. lags, 90 D. leads, 45
287. The voltage applied across an R-L circuit is equal to ____ of VR and VL.
A. arithmetic sum C. phasor sum B. algebraic sum D. sum of the squares
288. The power in an a.c. circuit is given by
A. VI cos φ C. I² Z
and power drawn is ____ watt.
A. 0.5 lead, 200 C. 0.866 lead, 173.2
B. 0.886 lag, 186.6 D. 0.5 lag, 50 292. The input of an a.c. circuit having p.f. of 0.8 lagging
is 20 kVA. The power drawn by the circuit is ____
kW.
A. 12 C. 16
B. 20 D. 8 293. The power factor of an a.c. circuit is given by
A. cosine of the phase angle
295. The phase angle of a series R-L-C circuit is leading if
A. XL = 0 C. XC > XL
B. R = 0 D. XC < XL
296. In an a.c. circuit, the ratio of kW/kVA represents A. power factor C. form factor B. load factor D. diversity factor 297. If p.f. of a circuit is unity, its reactive power is
A. a maximum C. zero 299. An alternating voltage e = 200 sin 314t is applied to
a device which offers an ohmic resistance of 20 Ω to the flow of current in one direction while entirely preventing the flow in the opposite direction. The average value of current will be
A. 5 A C. 1.57 A
B. 3.18 A D. 1.10 A
300. A 10 mH inductor carries a sinusoidal current of 1 A rms at a frequency of 50 Hz. The average power dissipated by the inductor is
A. 0 W C. 0.5 W 302. Power loss in an electrical circuit can take place in
A. inductance only B. capacitance only
C. inductance and resistance D. resistance only
303. A circuit of zero lagging power factor behaves as A. an inductive circuit C. R-L circuit B. a capacitive circuit D. R-C circuit
304. In an R-L series circuit the power factor is
A. leading C. zero
B. lagging D. unity
305. When a sinusoidal voltage is applied across an R-L series circuit having R = XL, the phase angle will be
A. 90° C. 45° leading
B. 45° lagging D. 90° leading 306. An ac source having voltage e = 110 sin (ωt + π/3) is
connected in an ac circuit. If the current drawn from the circuit varies as i = 5 sin (ωt - π/3) the impedance of the circuit will be
A. 22 Ω C. 30.8 Ω
B. 16 Ω D. none of these
307. Which are of the following true of the circuit shown in
307. Which are of the following true of the circuit shown in