AC Theory Practice Questions and Answers | Latest Version | 2024/2025 | Graded A+
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Course
AC Theory Practice
Institution
AC Theory Practice
AC Theory Practice Questions and
Answers | Latest Version | 2024/2025 |
Graded A+
What happens to the voltage and current in a purely resistive AC circuit?
In a purely resistive AC circuit, the voltage and current are in phase, meaning they reach
their maximum and minimum values at the sa...
AC Theory Practice Questions and
Answers | Latest Version | 2024/2025 |
Graded A+
What happens to the voltage and current in a purely resistive AC circuit?
✔✔ In a purely resistive AC circuit, the voltage and current are in phase, meaning they reach
their maximum and minimum values at the same time.
What is the role of inductance in an AC circuit?
✔✔ Inductance in an AC circuit opposes changes in current by creating a magnetic field that
induces a voltage opposite to the applied voltage, causing a phase shift where current lags behind
voltage.
How does capacitance affect an AC circuit?
✔✔ Capacitance in an AC circuit stores energy in the electric field and causes current to lead the
voltage, creating a phase shift where current reaches its peak before the voltage does.
What is impedance in an AC circuit?
✔✔ Impedance is the overall opposition to the flow of alternating current in a circuit, combining
the effects of resistance, inductance, and capacitance.
1
,Why does power dissipation occur in a resistive AC circuit but not in ideal capacitive or
inductive circuits?
✔✔ Power dissipation occurs in a resistive AC circuit because resistance converts electrical
energy into heat. In ideal capacitive or inductive circuits, energy is alternately stored and
returned to the circuit without loss.
How does the phase relationship between voltage and current affect power consumption in an
AC circuit?
✔✔ Power consumption in an AC circuit is maximized when voltage and current are in phase,
and minimized when they are completely out of phase, as less effective power is transferred.
What is the significance of the RMS (Root Mean Square) value in AC circuits?
✔✔ The RMS value is significant because it represents the effective or equivalent DC value of
an AC voltage or current, giving a more practical measure of the power delivered to a load.
What is the function of a transformer in AC circuits?
✔✔ A transformer changes the voltage level in an AC circuit by stepping it up or down through
electromagnetic induction, without altering the frequency.
2
,Why is AC commonly used for power transmission over long distances instead of DC?
✔✔ AC is commonly used for power transmission because it can be easily transformed to higher
voltages, which reduces power losses over long distances, making it more efficient than DC for
transmission.
What happens when the frequency of an AC supply increases in a circuit with inductance?
✔✔ When the frequency of an AC supply increases in a circuit with inductance, the opposition
to the current (inductive reactance) increases, making it harder for the current to flow.
What is meant by the term "power factor" in AC circuits?
✔✔ Power factor refers to the ratio of real power (the power used to perform work) to apparent
power (the total power supplied), and it indicates how efficiently electrical power is being used.
How do AC generators produce alternating current?
✔✔ AC generators produce alternating current by rotating a coil of wire within a magnetic field,
causing the direction of the induced current to reverse periodically as the coil rotates.
What is the role of phase in an AC circuit with multiple loads?
3
, ✔✔ The phase in an AC circuit with multiple loads determines how the voltage and current
waveforms align or misalign, affecting power distribution and overall circuit performance.
What effect does adding capacitance have on the power factor in an inductive AC circuit?
✔✔ Adding capacitance to an inductive AC circuit improves the power factor by offsetting the
phase lag caused by inductance, bringing the voltage and current more in phase.
How does a capacitor behave at very high frequencies in an AC circuit?
✔✔ At very high frequencies, a capacitor in an AC circuit offers very little opposition to the
flow of current, essentially acting like a short circuit.
What is the purpose of using a capacitor in an AC motor?
✔✔ A capacitor in an AC motor is used to create a phase shift between the windings, helping to
start and run the motor by producing the necessary rotating magnetic field.
What is the effect of increasing inductance in an AC circuit on current flow?
✔✔ Increasing inductance in an AC circuit causes the current to decrease because the inductive
reactance opposes the current more as the inductance increases.
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