In a purely resistive circuit, how is current related to the applied source voltage?

In a purely resistive circuit, the relationship between current and the applied source voltage is defined by Ohm's Law, which states that the current flowing through a resistor is directly proportional to the voltage across it, provided the resistance remains constant.

When we say that current is in phase with the voltage, it means that the peaks and troughs of the current and voltage waveforms occur at the same time. In practical terms, when the voltage reaches its maximum, the current also reaches its maximum simultaneously, and when the voltage is at zero, the current is also at zero. This synchronous behavior is characteristic of resistive circuits, where there is no phase shift due to inductive or capacitive elements that would cause the current to lead or lag the voltage.

Understanding this relationship is crucial for analyzing circuits and ensures that when designing or troubleshooting resistive circuits, you can predict how changes in voltage affect the current directly and proportionally.