ALTERNATING CURRENT

All of the following have the same units except:

• inductance.

• capacitive reactance.

• impedance.

• resistance.

A resistor is connected to an AC power supply. On this circuit, the current

• leads the voltage by 90°.

• lags the voltage by 90°.

• is in phase with the voltage.

• none of the given answers

A pure inductor is connected to an AC power supply. In this circuit, the current

• leads the voltage by 90°.

• lags the voltage by 90°.

• is in phase with the voltage.

• none of the given answers.

If the frequency of the AC voltage across an inductor is doubled, the inductive reactance of that inductor

• increases to 4 times its original value.

• increases to twice its original value.

• decreases to one-half its original value.

• decreases to one-fourth its original value.

A pure capacitor is connected to an AC power supply. In this circuit, the current

• leads the voltage by 90°.

• lags the voltage by 90°.

• is in phase with the voltage.

• none of the given answers

What is the phase angle between the voltages of the inductor and capacitor in a RLC series circuit?

• zero

• 90°

• 180°

• 270°

The power factor of an RLC circuit is defined as cos ∅ = R/Z, but the phase angle can also be calculated from ________.

• sin ∅ = (XL - XC)/Z

• sin ∅ = (XL - XC)/RZ

• sin ∅ = Z/(XL - XC)

• sin ∅ = RZ/(XL - XC)

Consider an RLC circuit that is driven by an AC applied voltage. At resonance,

• the peak voltage across the capacitor is greater than the peak voltage across the inductor.

• the peak voltage across the inductor is greater than the peak voltage across the capacitor.

• the current is in phase with the driving voltage.

• the peak voltage across the resistor is equal to the peak voltage across the inductor.

A capacitor 120 µF is connected to an AC source of 6 V with frequency 100 Hz. If the frequency is increased to 200 Hz, the reactance of the capacitor will be

• half the original value.

• same as the original value.

• two times the original value.

• the reciprocal of the original value.

If an electric bulb is connected to an AC source, which of the following statement is true about the phase difference between the voltage across the bulb and current flowing in it?

• In phase.

• Not in phase.

• The voltage is leading the current.

• The current is leading the voltage.