When are the current and voltage in a circuit considered to be in phase?

Current and voltage are considered to be in phase when their waveforms reach their respective maximum (positive peak) and minimum (negative peak) values simultaneously. This means that, at any given time, the current and voltage values rise and fall together, which is characteristic of purely resistive circuits. In such circuits, the phase difference between current and voltage is zero degrees, ensuring that they reach their peaks at the same time.

The other choices do not accurately describe the condition of being in phase. For example, if the current is larger than the voltage, it doesn't indicate anything about their phase relationship; it merely comments on their magnitudes. Similarly, if the voltage leads the current, it implies a phase difference where voltage reaches its peak before the current, which is typical in inductive circuits, not purely resistive ones. Thus, the scenario where positive and negative peaks occur simultaneously best illustrates the concept of being in phase.