What best defines a branch circuit that has equal voltage between the grounded and ungrounded conductors?

A branch circuit that has equal voltage between the grounded and ungrounded conductors is best defined as a multiwire circuit. This type of circuit typically consists of two or more ungrounded conductors sharing a single neutral conductor. In a properly connected multiwire circuit, the voltages between the grounded (neutral) and ungrounded conductors are balanced, which allows for efficient operation and reduced circuit loading.

In this configuration, it is essential that the conductors originate from different phases of the supply system to ensure they can be effectively combined while maintaining equal voltage levels across them. This allows the circuit to share the neutral effectively, as the return current can be minimized when the loads on the ungrounded conductors are balanced.

Understanding the concept of multiwire circuits is crucial for ensuring compliance with electrical codes and maintaining the safety and efficiency of electrical installations.