Electrical Engineering · Question Bank

1P AC Circuits

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#41📜 EE Pre-Board August 2015📘 PowerhouseEasy

What is the ac current in a circuit if the impedance is (5 + j4) Ω and the voltage source, \(V_{rms}\), is 10 V?

A\(2.04\angle 38.7^\circ\) A

B\(1.56\angle -38.7^\circ\) A

C\(1.25\angle 54.3^\circ\) A

D\(1.11\angle -42.6^\circ\) A

#42📜 EE Pre-Board August 2015📘 PowerhouseEasy

If the capacitance in a series RLC ac circuit increases by a factor of 4, what happens to the resonant frequency?

AIt doubles

BIt stays the same

CIt decreases by 50%

DIt increases by 50%

#43📜 EE Pre-Board August 2015📘 PowerhouseEasy

In a series RL circuit, R = 20 Ω and L = 0.06 H. The current lags the voltage by 80°. Determine ω.

A1,890 rad/sec

B328 rad/sec

C1,980 rad/sec

D823 rad/sec

#44📜 EE Pre-Board August 2015📘 PowerhouseEasy

An alternating current is represented by \(i = 70.7\sin 520t\). Determine the value of the current 0.0015 second after passing through zero and increasing positively.

A49.7 A

B0.96 A

C24.8 A

D74.9 A

#45📜 EE Pre-Board August 2015📘 PowerhouseEasy

A complex current wave is represented by the equation \(i = 5 + 5\sin(120\pi t)\) A. Find its average value in amperes.

A4.5

#46📜 EE Pre-Board March 2016📘 PowerhouseEasy

A 15 ohm resistor connected in series with an inductor has an equivalent impedance of 30 ohms with an unknown angle. Find the power factor angle in degrees.

A30

B60

C45

D75

#47📜 EE Pre-Board March 2016📘 PowerhouseEasy

Transform the current given by 6 + j8 A to its time domain.

A\(100\cos(\omega t + 53.13^\circ)\)

B\(10\cos(\omega t + 53.13^\circ)\)

C\(100\cos(\omega t + 36.87^\circ)\)

D\(10\cos(\omega t + 36.87^\circ)\)

#48📜 EE Pre-Board March 2016📘 PowerhouseEasy

What is the equivalent phasor of \(i(t) = 20\cos(\omega t + 40^\circ)\) A?

A15.3 − j12.9 A

B−15.3 + j12.9 A

C15.3 + j12.9 A

D−15.3 − j12.9 A

#49📜 EE Pre-Board March 2016📘 PowerhouseEasy

A parallel RL circuit draws a total current of 17A and 1.8KW from a 120V supply. Find R.

A7 ohms

B8 ohms

C9 ohms

D10 ohms

#50📜 EE Pre-Board March 2016📘 PowerhouseEasy

A 6 ohm resistor is connected in series with an inductor L across a 110 V, 60 Hz source and draws a current of 10 A. Find L.

A25.5 mH

B26.5 mH

C23.5 mH

D24.5 mH

#51📜 EE Pre-Board March 2016📘 PowerhouseEasy

What capacitance must be placed in series with an inductance of 0.05 henry, so that when the frequency is 100 Hz, the impedance becomes equal to the ohmic resistance?

A50.7 μF

B31.8 μF

C67.5 μF

D42 μF

#52📜 EE Pre-Board March 2016📘 PowerhouseEasy

If the waveform of a current has form factor 1.2 and peak factor 1.7, find the average value of the current if the maximum value of the current is 100 A.

A45 A

B47 A

C49 A

D51 A

#53📜 EE Pre-Board March 2016📘 PowerhouseMedium

A coil with 40 ohm resistance and 0.02 H inductance and a pure capacitor are connected in parallel across a 60 Hz supply. Find the value of the capacitor in uF if the circuit is resonant.

A14.35

B12.07

C11.67

D15.82

#54📜 EE Pre-Board March 2017📘 PowerhouseEasy

Find the reactive factor of the load having 30 kW and 50 kVA.

A0.6

B0.5

C0.8

D0.7

#55📜 EE Pre-Board March 2017📘 PowerhouseEasy

What is the frequency where the reactances of 57 μH inductor and a 57 μF capacitor are equal?

A7.92 kHz

B9.72 kHz

C2.79 kHz

D2.97 kHz

#56📜 EE Pre-Board March 2017📘 PowerhouseEasy

A resistance of 30 Ω and a capacitance of 132.6 μF are connected in series across a 220 V, variable frequency ac supply. At what frequency in Hz will the current be 4.4 A?

A30 Hz

B40 Hz

C50 Hz

D60 Hz

#57📜 EE Pre-Board March 2017📘 PowerhouseEasy

An inductive coil consumes 500 W of power at 10 A and 110 v and 60 Hz. Determine the inductance of the coil.

A24 mH

B25 mH

C26 mH

D27 mH

#58📜 EE Pre-Board March 2017📘 PowerhouseEasy

A parallel RLC circuit has R = 0.5 Ω, L = 10 mH and C = 2.5 mF. Determine the resonance frequency.

A63.66 Hz

B79.79 Hz

C112.82 Hz

D31.83 Hz

#59📜 EE Pre-Board March 2017📘 PowerhouseMedium

Three sinusoidal generators and a battery are connected in series with a coil whose resistance and inductance are 8 Ω and 26.53 mH, respectively. The frequency and rms voltage of the respective generators are 20 Hz, 15 V; 60 Hz, 30 V; and 80 Hz, 50 V. The battery voltage is 6 V. Determine the circuit rms voltage.

A10 v

B60.51 v

C101 v

D69.5 v

#60📜 EE Pre-Board August 2017📘 PowerhouseEasy

At what frequency will a 100 μF capacitor offer a reactance of 100 Ω?

A159 Hz

B15.9 Hz

C1.59 Hz

D31.8 Hz

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