A wave with amplitude y
The amplitude of a (periodic) vibration is the biggest deviation from the equilibrium position, or, in other words, the maximum result. The vibration may be a mechanical vibration of, for example, a harp string, or the sound wave generated, or any other cyclically-varying phenomenon. Because a wave phenomenon always varies in size, the value of that wave will also vary. The amplitude is now the value from equilibrium to the maximum rash or strength of the wave.
The amplitude of an electrical voltage is the maximum value of the voltage. This amplitude is measured in volts. Although the mains voltage of the household power grid is about 230 V, this is the effective value. The amplitude is a factor √2 larger.
The amplitude of a pendulum is the distance from the neutral center (equilibrium position) to the greatest outcome. This amplitude is measured in meters.
The amplitude of sound is the maximum pressure that occurs. This is measured in Pascal.
The "strength" of a sinusoidal wave is entirely determined by the amplitude. Other shapes still have features such as the form factor and the effective value.
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