What waveform is characterized by three waveforms alternating between positive and negative?

The correct response describes a three-phase unrectified waveform, which consists of three distinct waveforms that alternate in a sinusoidal manner between positive and negative voltages. In a three-phase system, these waveforms are offset by 120 degrees, meaning that when one phase is at its peak positive value, the others will be at different points in their cycles, creating a more constant and balanced power delivery. This configuration is essential in various industrial applications as it provides smoother operation of motors and reduces the overall risk of voltage drops.

Three-phase systems are commonly used because they deliver continuous power without the dips and surges that can occur in single-phase systems. The steady nature of the voltage in a three-phase system allows for more efficient operation in electrical equipment, making it preferable in many high-energy applications.