MCQ – AC Fundamentals Results #1. In a pure inductor the voltage wave form leads the current by...? 120* 120* 90* 90* 180* 180* 60* 60* #2. The form factor of sinusoidal wave form is....? 1.11 1.11 1.57 1.57 3.14 3.14 1.414 1.414 #3. The instataneous voltage across a pure resistor is.... with current? in phase in phase lags lags out of phase out of phase leads leads #4. The reciprocal of frequency is known as....? time constant time constant amplitude amplitude resonance resonance time period time period #5. Reactive power is given by....? VI Sin $ VI Sin $ VI VI VI Cos$ VI Cos$ VIR VIR #6. Form factor is the ratio of....? rms value / average value rms value / average value average value x rms value average value x rms value instantaneous value x rms value instantaneous value x rms value average value / rms value average value / rms value #7. The power factor of the inductive loading is....? unity unity lagging lagging leading leading zero zero #8. Impedance at series resonance circuit is....? maximum maximum minimum minimum average average none of the above none of the above #9. Power factor is defined as....? kW/kVA kW/kVA kW/kVR kW/kVR kVAR/kVA kVAR/kVA kVA/kW kVA/kW #10. In a AC series circuits Q factor is....? cos$ cos$ 1/sin$ 1/sin$ sin$ sin$ 1/cos$ 1/cos$ #11. Power factor of R-C series circuit is.....? 1 1 between 0 and 1 between 0 and 1 0 0 greater than 1 greater than 1 #12. Capacitive reactance is......? inversely proportional to frequency inversely proportional to frequency directly proportional to frequency directly proportional to frequency directly proportional to capacitance directly proportional to capacitance independent of frequency independent of frequency #13. The ratio of Z/R is.....? power factor power factor form factor form factor reciprocal of power factor reciprocal of power factor reciprocal of form factor reciprocal of form factor #14. Admittance is the reciprocal of....? resistance resistance impedence impedence susceptance susceptance reactance reactance #15. The power factor of ordinary electric bulb is...? slightly less than one slightly less than one slightly more than one slightly more than one one one zero zero #16. Unit of inductive reactance is....? weber weber hentry hentry ohm ohm milli hentry milli hentry #17. Peak factor of a sinusoidal wave form is....? 1.41 1.41 1.21 1.21 1 1 1.11 1.11 #18. The rms value of a sine wave is 100A. Its peak value is...? 160 A 160 A 200 A 200 A 141 A 141 A 100 A 100 A #19. The power factor of an AC circuit is equal to.....? unity for a resistive circuit unity for a resistive circuit sine of the phase angle sine of the phase angle cosine of the phase angle cosine of the phase angle one one #20. Unit of reactive power is....? watt watt VAR VAR ohm ohm VA VA #21. With in the increase in applied frequency, the dielectric loss will be....? same same decrease decrease one half one half increase increase #22. With in the increase in applied frequency, the dielectric loss will be....? increase increase decrease decrease one half one half same same #23. Q factor of a series R-L-C circuit possessing resonant frequency of 10 Hz and band width of 5 Hz is...? 2.5 2.5 4 4 5.5 5.5 2 2 #24. Power factor of an inductive circuit is usually improved by adding a capacitor to it in....? series series either in series or parallel either in series or parallel parallel parallel #25. Form factor of a full rectified sine wave is...? 1.11 1.11 1.41 1.41 1.571 1.571 1 1 #26. Form factor of a half rectified sine wave is...? 1.41 1.41 1.571 1.571 1.11 1.11 1 1 rms / average = (Vm/2)/(Vm/pi) = 1.571 #27. An alternating current is given by i=14.14sin377t. find its rms value of current? 10 A 10 A 24 A 24 A 15 A 15 A 14.14 A 14.14 A 14.14/1.4 = 10A #28. The ratio of maximum value to the rms value of an alternating quantity is called....? peak factor peak factor form factor form factor average value average value mean value mean value #29. A seris RL circuit has a resistance of 30 ohms and an inductance of 40 ohms. The impedence is....? 40 ohms 40 ohms 90 ohms 90 ohms 70 ohms 70 ohms 50 ohms 50 ohms Root of 900 1600 = 50 #30. The unit of capacitance is....? hentry hentry ohm ohm farad farad watt watt #31. Two capacitors of 8 micro farad each are connected in series. the total capacitance is....? 4 mF 4 mF 8 mF 8 mF 10 mF 10 mF 16 mF 16 mF 8/2=4 #32. Capacitance is not affected by...? plate area plate area dielectric material dielectric material distance between plates distance between plates frequency frequency #33. Two capacitors of 10 micro farad each are connected in parallel. the total capacitance is....? 20 mF 20 mF 10 mF 10 mF 5 mF 5 mF 100 mF 100 mF #34. The capacitors opposition to alternating current is called...? capacitive reactance capacitive reactance resistance resistance capacitance capacitance impedence impedence #35. In a capacitive AC circuit is the.....? none of the above none of the above current is inphase with voltage current is inphase with voltage current laggs voltage current laggs voltage current leads voltage current leads voltage #36. Which condition is called as resonance RLC circuit? XL= XC XL= XC XL > XC XL > XC XL< XC XL< XC #37. The line voltage in three phase delta connection is....? Twice as phase voltage Twice as phase voltage none of these none of these same as the phase voltage same as the phase voltage Thrice as phase voltage Thrice as phase voltage #38. The line current in three phase star connection is....? Thrice as phase current Thrice as phase current none of these none of these same as the phase current same as the phase current Twice as phase current Twice as phase current #39. Potential inside a hollow sphere charged with a voltage V is....? 0 0 V/2 V/2 V V 2V 2V #40. The reciprocal of impedance is...? susceptance susceptance resistance resistance admittance admittance conductance conductance #41. Phase sequence is the order of attaining? RMS value RMS value None of the above None of the above Maximum value Maximum value Average value Average value #42. In a R.L.C series resonant circuit....? R=XL R=XL R=XC R=XC XL>XC XL>XC R=Z R=Z #43. Two possible phase sequences are....? BRY,RYB BRY,RYB RYB,RBY RYB,RBY RYB,YBR RYB,YBR RBY,YRB RBY,YRB #44. In a RLC resonant circuit magnification is.....? Z Z WL/R WL/R WLC WLC WL WL #45. Three phase inter connection used in 3 phase 4 wire distribution system is.....? star star star star delta delta delta delta delta delta star star finish
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