AC Fundamentals

Which of these frequencies has the shorter period?

• 1 Krad/s

• 1 Khz

The voltage across an inductor leads the current

through it by 90◦.

• Yes

• No

If v₁ = 30 sin(ωt + 10^◦) and v₂ = 20 sin(ωt + 50^◦),

which of these statements are true?

• v₁ leads v₂

• v₂ leads v₁

• v₂ lags v₁

• v₁ lags v₂

• v₂ and v₁ are in phase

The imaginary part of impedance is called:

• resistance

• admittance

• susceptance

• conductance

• reactance

At what frequency will the output voltage v_o(t) in

Fig. be equal to the input voltage v(t)?

• 0 rad/s

• 1 rad/s

• 4 rad/s

• ∞rad/s

• none of the above

A series RC circuit has V_R = 12 V and V_C = 5 V.

The supply voltage is

A series RCL circuit has R = 30 Ohm, ,XC = −50 Ohm,
and XL = 90 Ohm,. The impedance of the circuit is:

• 30 + j140  Ohm

• 30 + j40 Ohm

• 30 − j40 Ohm $\Omega$  

•  −30 − j40  $\Omega$  

•  −30 + j40  $\Omega$  

All definitions of power factor of a series R-L-C circuit are correct except

• Ratio of net reactance and impedance

• Ratio of kW and kVA

• Ration of Resistance and Reactance

• Ratio of kW and kVAR

If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is

• Sine wave of same frequency

• Sine wave of half the original frequency

• Sine wave of double the original frequency

• Not a sine wave

Form factor for a sine wave is