Which statement describes the relationship between RMS and peak voltage in a sine wave?

• A. RMS is the effective value, while peak is the maximum amplitude.
• B. RMS is equal to peak voltage.
• C. RMS is always greater than peak voltage.
• D. RMS is half the peak voltage.

Answer: (A)

RMS represents the effective value of an AC signal—the DC amount that would produce the same heating effect in a resistor. For a sine wave, the peak value is the highest instantaneous voltage you reach. The RMS value for a sine wave is the peak voltage divided by the square root of 2, which is about 0.707 of the peak. So the statement that RMS is the effective value while peak is the maximum amplitude correctly captures their roles and their relationship.

Why the other ideas don’t fit: the RMS value is not equal to the peak for a sine wave (unless the peak is zero); it is not greater than the peak (it is less than the peak by a factor of about 0.707); it is not simply half the peak.