What remains constant in a parallel circuit?

In a parallel circuit, the branch voltage remains constant. This means that each component connected in parallel experiences the same voltage across it, regardless of the resistance of each branch. This is a fundamental property of parallel circuits, where voltage is distributed equally among all branches.

When you consider a simple parallel circuit where multiple resistors are connected across the same two terminals, each resistor experiences the same voltage drop. This is crucial in applications like cathodic protection systems where maintaining a consistent voltage across multiple components is essential for their proper functioning, ensuring that each component receives the correct potential for effective protection against corrosion.

In contrast, the current is divided among the branches, leading to different current values depending on the resistance of each branch. The overall resistance of a parallel circuit decreases as more branches are added, and total power is the sum of power consumed in all branches, which can vary. Thus, the constant nature of the branch voltage is what makes it the correct answer in a parallel circuit context.