When an AC voltage is applied to a circuit and both voltage and current reach their maximum values simultaneously, what is their relationship called?

When an AC voltage is applied to a circuit and both the voltage and current reach their maximum values simultaneously, this condition is referred to as being "in phase."

In an AC circuit, being in phase means that the peaks and zero crossings of the voltage wave occur at the same times as those of the current wave. This results in both waveforms exhibiting the same frequency and periodicity, leading to maximum power transfer and efficient energy use in the circuit. In this scenario, the two signals coincide perfectly, and there's no time delay between them. As a result, the voltage and current can reinforce each other, maximizing the power delivered to the load.

Understanding this relationship is crucial in power engineering, particularly in the analysis of power factor, where the goal is often to minimize phase shifts between voltage and current to ensure efficient circuit operation.