In a circuit with resistance alone, what is the relationship between current and voltage?

In a circuit that consists solely of resistance, current and voltage are said to be in phase. This means that the current reaches its maximum value at the same time as the voltage does, and both waveforms peak simultaneously. The relationship arises from Ohm's Law, which states that voltage (V) equals current (I) multiplied by resistance (R), or V = I × R. Because resistance does not introduce any reactive elements (like inductance or capacitance), there is no phase difference between the voltage and the current.

In contrast, options that refer to phase differences (like "out of phase," "lagging," and "leading") pertain to circuits that include reactive components (inductors or capacitors), where the current can either lag behind or lead the voltage. These distinctions are important in alternating current (AC) circuits but do not apply in the context of pure resistive circuits, where the concept of being "in phase" is predominant.