Question 1

Why do countries use AC for mains electricity instead of DC?

Accepted Answer

AC is favoured for mains power primarily because its voltage can be easily stepped up or down using transformers. This allows for high-voltage, low-current transmission over long distances, which significantly reduces power loss ($P=I^2R$) in the cables.

Question 2

What's the difference between frequency ($f$) and angular frequency ($\omega$)?

Accepted Answer

Frequency ($f$) is the number of complete cycles per second, measured in Hertz (Hz). Angular frequency ($\omega$) describes the rate of change of the phase angle of the waveform, measured in radians per second (rad s⁻¹). They are related by $\omega = 2\pi f$, where $2\pi$ is the number of radians in one full cycle.

Question 3

Is the RMS value always $V_{peak}/\sqrt{2}$ for any alternating current?

Accepted Answer

No, this specific relationship ($V_{rms} = V_{peak}/\sqrt{2}$) is only valid for **sinusoidal** alternating currents. For other waveform shapes (e.g., square waves, triangular waves), the relationship between RMS and peak values is different.

Characteristics of alternating currents

What you need to know

Characteristics of alternating currents