The amplitude of an alternating quantity refers to the maximum magnitude or value reached by that quantity during its oscillation or cycle. It represents the peak or maximum value of the alternating quantity.
In the context of alternating current (AC) electricity, which is a common example of an alternating quantity, the amplitude is often referred to as the peak value or peak amplitude. It indicates the maximum magnitude of the current or voltage during one complete cycle of oscillation. For example, if the peak value of an AC voltage is 10 volts, it means that the voltage reaches a maximum value of 10 volts during each cycle.
It's important to note that the amplitude of an alternating quantity is different from its average or RMS (Root Mean Square) value. The RMS value is a measure of the effective or equivalent steady-state value of the alternating quantity, whereas the amplitude represents the maximum magnitude of the oscillation.