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Ac basic
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q21 ⇒ Under the conditions of maximum power transfer from an ac
source to a variable load the sum of the source reactance and load reactance is zero [other wrong options] [Discuss in forum] the load impedance must also be inductive, if the generator
impedance is inductive the sum of the source and the load impedances is zero. the load impedance has the same phase angle as the generator impedance. |
Q22 ⇒ A lamp load is given a supply from 3-phase-4-wire. 2 30/400 V ac
supply system. Ifa three phase motor is now switched on across
the same supply, then neutral current will remain unchanged. [other wrong options] [Discuss in forum] increase. decrease. unpredictable. |
Q23 ⇒ Phase reversal in a 4-wire unbalanced load supplied from a balanced
3-phase supply causes change in magnitude as well as phase angle of the neutral current, [other wrong options] [Discuss in forum] the power consumed. magnitude of phase currents only the magnitude of the neutral current. |
Q24 ⇒ If an ac voltage wave is corrupted with an arbitrary number of
harmonics, then the overall voltage waveform differs from its
fundamental frequency component in terms of all the three measures (peak, rms, and average values). [other wrong options] [Discuss in forum] only the peak values. only the rms values. only the average values |
Q25 ⇒ For ade voltage an indcutor is virtually a short circuit. [other wrong options] [Discuss in forum] is an open circuit. depends on polarity. depends on voltage value |
Q26 ⇒ Nonlinear system cannot be analysed by Laplace transform because it has no zero initial conditions. [other wrong options] [Discuss in forum] superpositon law cannot be applied. non-linearity is generally not well defined. all of the above |
Q27 ⇒ If two sinusoids of the same frequency but of different amplitudes
and phase difference are added, the resultant is a sinusoid of the same frequency. [other wrong options] [Discuss in forum] sinusoid of double the original frequency. sinusoid of half the original frequency. non-sinusoid. |
Q28 ⇒ A circuit component that opposes the change in circuit voltage is capacitance. [other wrong options] [Discuss in forum] resistance. inductance. all of the above |
Q29 ⇒ Skin effect occurs when a conductor carries current at____frequencies. high [other wrong options] [Discuss in forum] very low low |
Q30 ⇒ In an ac series RLC circuit, the voltage across R and L is 20 V,
voltage across L and C is 9 V and voltage across RLC is 15 V.
What is the voltage across C? 7 V [other wrong options] [Discuss in forum] 12 V 16 V 21 V |
Q31 ⇒ Under the condition of resonance in R-L-C series circuit, the pf of
the circuit is unity. [other wrong options] [Discuss in forum] 0.5 lagging. 0.5 leading. zero. |
Q32 ⇒ A series R-L-C circuit, excited by a 100 V variable frequency
source, has a resistance of 10 ω and an inductive reactance of
50 ω at 100 Hz. If the resonance frequency is 500 Hz, what is the
voltage across the capacitor at resonance? 2,500 V [other wrong options] [Discuss in forum] 100 V 500 V 5,000 V |
Q33 ⇒ coil is tuned to resonance at 500 kHz with a resonating capacitor
of 36 pF at 250 kHz, the resonance is obtained with resonating
capacitor of 160 pF. What is the self-capacitance of the coil ? 5.33 pF [other wrong options] [Discuss in forum] 2.66 pF 8 pF 10.66 pF |
Q34 ⇒ In order to tune a parallel resonant circuit to a lower frequency, the
capacitance must be increased [other wrong options] [Discuss in forum] be decreased be zero. remain the same. |
Q35 ⇒ The rated voltage of a 3-phase power system
is given as rms line-to-line voltage [other wrong options] [Discuss in forum] rms phase voltage. peak phase voltage peak line-to-line voltage |
Q36 ⇒ The power measurement in balanced three-phase circuit can be
done by any one of the above [other wrong options] [Discuss in forum] one wattmeter method only. two wattmeters method only. three wattmeters method only |
Q37 ⇒ Three unequal impedances are connected in delta to a 3-phase,
3-wire system Both of the phase currents and line currents will be unbalanced. [other wrong options] [Discuss in forum] The voltages across the three phases will be different. Phase currents will be unbalanced but the line currents will be balanced. None of the above |
Q38 ⇒ what is the average power for periodic non-sinusoidal voltages
and currents ? The sum of the root mean square power of the sinusoidal components including the fundamental. [other wrong options] [Discuss in forum] The average power of the fundamental component alone. The sum of the average powers of the harmonics excluding the fundamental. The sum of the average powers of the sinusoidal components including the fundamental |
Q39 ⇒ Inductance affects the flow of direct current at the time of turning on and off. [other wrong options] [Discuss in forum] turning off. turning on. none of the above. |
Q40 ⇒ The impulse response of an R-L circuit is a decaying exponential function. [other wrong options] [Discuss in forum] rising exponential function. step function. parabolic function. |
Or |