What is the phase relationship between current and voltage in an AC circuit?

The phase relationship between current and voltage in an AC circuit is determined by the type of circuit.

In a purely resistive circuit, the current and voltage are in phase with each other, meaning they reach their maximum and minimum values at the same time. This is because the current is directly proportional to the voltage, according to Ohm's Law.

In an inductive circuit, such as a coil or transformer, the current lags behind the voltage by 90 degrees. This is because the magnetic field generated by the changing current induces a voltage in the opposite direction, which opposes the original voltage and causes a delay in the current.

In a capacitive circuit, such as a capacitor, the current leads the voltage by 90 degrees. This is because the capacitor stores energy in an electric field, which causes a voltage to build up across it. As the voltage increases, the current also increases, but with a delay due to the charging time of the capacitor.

In a circuit with both inductive and capacitive elements, the phase relationship between current and voltage can be more complex, depending on the frequency and magnitude of the AC signal. This can lead to resonance and other phenomena that must be carefully analysed in order to design and operate the circuit effectively.