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Q 1/30
Score 0
The power factor of a load connected to a 120V, 60 Hz supply is raised from 0.707 to 0.866 lagging by connecting a 53 µF capacitor across the load. What is the true power of the load in watts?
30
712.7
656.5
722.6
680.7
Q 2/30
Score 0
A 220 V, 10 hp, 60 Hz, single phase induction motor operates at an efficiency of 86% and power factor of 90%. What capacitance of capacitor in µF should be connected across the motor terminals in order to bring the total power factor to unity?
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120
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230
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30 questions
Q.
The power factor of a load connected to a 120V, 60 Hz supply is raised from 0.707 to 0.866 lagging by connecting a 53 µF capacitor across the load. What is the true power of the load in watts?
1
30 sec
Q.
A 220 V, 10 hp, 60 Hz, single phase induction motor operates at an efficiency of 86% and power factor of 90%. What capacitance of capacitor in µF should be connected across the motor terminals in order to bring the total power factor to unity?
2
30 sec
Q.
A series circuit consists of C = 30 µF and R = 50 ohms are connected across 110 V, 60 Hz source. Find the voltage across C in volts.
3
30 sec
Q.
Two impedances Z1 = 10 + jX and Zâ‚‚ = R + j0, all in ohms are connected in parallel. Find the value of X in ohms so that the total impedance is 8 + j4 ohms.
4
30 sec
Q.
An unbalanced wye-connected load with impedances of Za = 10 + j5 ohms, Zb = 8 + j4 ohms and Zc = 20 + j20 ohms is supplied by a 3 phase, 4-wire abc system. If the line to neutral voltage is 120 V, find the total power in watts.
5
30 sec
Q.
Three 100μF capacitors are connected in delta to a 500 volt, three phase 50 HZ supply. Find the line current.
6
30 sec
Q.
A 25 ohm resistance has an average power of 400 watts. Determine the maximum value of the current function if it is triangular.
A parallel branch circuit composed of a 100 ohm resistance, 150 ohm capacitance reactance and 90 ohm inductive reactance. What is the total impedance of the circuit?
9
30 sec
Q.
A 200 ohm resistor, a 0.04 henry inductor and a 0.25 microfarad capacitor are connected in series. What is the voltage across the combination if the current of 10 + j10 ma is applied at ω = 10,000 rad per second?
10
30 sec
Q.
A resistance of 30 is in series with inductance of 30 mH. What is the frequency in hertz (HZ) so that the power factor angle is 60° lagging?
A parallel RLC circuit has a resonant frequency of 20,000 rad/sec. If C is equal to 1 μF, find the value of L.
13
30 sec
Q.
A sinusoidal current having peak value of 7.07 A is superimposed in dc of 5 A. If a hotwire ammeter is used to measure the combined current in the circuit, it will indicate__ amperes.
14
30 sec
Q.
A balance wye-connected load of 30 + j10 ohms per phase is connected to a 3 phase 60 HZ 208 volts supply. Determine the value of each capacitor in mF which will yield unity power factor.
15
30 sec
Q.
A voltage source of 50 cos 1000t is in series with a kilo ohm resistor and a 1-microfarad capacitor. What is the circuit current?
16
30 sec
Q.
An inductive load consisting of R and X in parallel feeding from a 2.4 KV rms supply, absorbs 288 KW at a lagging power factor of 0.80. What is the value of R in ohms?
17
30 sec
Q.
Determine the current drawn from a three-phase, 440 v line by a three-phase 15 hp motor opening at full load, 90% efficiency and 80% power factor lagging.
18
30 sec
Q.
The wye-connected 3 phase voltage source has V sub c = 115 v rms with -240 degrees angle. Find the line to line voltage V sub bc.
19
30 sec
Q.
A coil has a resistance of 3 Ω and an inductance of 0.01 H is connected in series with a capacitor across a voltage source of 220 volts. What must be the capacitance of the capacitor in order that maximum current occurs at 60 Hz?
20
30 sec
Q.
What is the power given V = 4 sin 3t?
21
30 sec
Q.
A coil of 50 ohm resistance and 150 mH inductance is connected in parallel with a 50- µF capacitor. What is the power factor of the circuit?
22
30 sec
Q.
An inductance of 20 mH is connected in parallel with a capacitance of 80 ΩF. What is the frequency when XL= Xc?
23
30 sec
Q.
An inductive coil consumes active power of 500 w and draws 10 A from a 60 Hz ac supply of 110 v. What is the coil inductance?
24
30 sec
Q.
A coil having a resistance of 10 Ω and an inductance of 0.1 H is connected in series with a 75 µF capacitor across a voltage source of 220 volts. Calculate the Q-factor of the circuit.
25
30 sec
Q.
An inductive coil consumes active power of 500 w and draws 10 A from a 60 Hz ac supply of 110 v. What is the coil inductance?
26
30 sec
Q.
An inductive load draws a current of 6 A at 0.8 p.f. from a 208 v, 60 Hz source. If a capacitor of 5x10^-5 F is connected in parallel with the load, what is the overall p.f.?
27
30 sec
Q.
A coil with L=2H and R = 362 Ω is connected to a 230-v, 50 HZ supply. Calculate the energy stored when the instantaneous voltage is zero.
28
30 sec
Q.
A 40 microfarad capacitor is connected in parallel with 40 ohm resistor. What power is drawn when source voltage is V = 220 sin ωt volts?
29
30 sec
Q.
A coil having an inductance of 0.05 H and resistance of 10 ohms is connected in series w/ a 25 µF capacitor across a 220 V ac source. What is the resonance frequency of the circuit?
