Balance of charge implies

• A. The charges are the same size and will cancel if balanced
• B. Balanced charge has no effect on tissue response
• C. Amplitude determines total charge
• D. Polarity direction is the only factor

Answer: (A)

Balance of charge means the net electrical charge delivered in a complete cycle is zero because the positive and negative charges are equal in amount and opposite in direction. When a biphasic pulse has equal magnitude of charge in each phase, the charges cancel, so there’s no buildup of net charge at the electrode-tissue interface. This reduces electrode polarization and unwanted chemical changes, making the stimulation safer and more comfortable.

That’s why the statement describing equal, opposite charges that cancel is the best answer. Balanced charge doesn’t mean there’s no tissue response at all—it reduces adverse effects from polarization. Total charge depends on both amplitude and duration of each phase, so amplitude alone doesn’t guarantee balance. And polarity direction matters, but it isn’t the sole factor; balance requires equal opposite charges, not just the direction.