What is meant by duty cycle in pulse-width modulation?

Duty cycle in pulse-width modulation (PWM) is defined as the ratio of the time a signal remains in the 'on' state compared to the total time of a single cycle. This measurement is typically expressed as a percentage. For instance, if a PWM signal is on for 2 milliseconds and off for 8 milliseconds, the total period is 10 milliseconds and the duty cycle would be 20%.

This concept is crucial in applications such as motor speed control and light dimming, where controlling the average power delivered to a device is necessary. By varying the duty cycle, you can effectively control the perceived intensity or speed without altering the frequency of the signal, thus influencing performance outcomes without introducing additional complexity in the circuit design.

The other options highlight different signal characteristics that are not related to the duty cycle. Frequency and amplitude relate to how often the signal oscillates and how strong the signal is respectively, while total energy delivered in one cycle measures the overall power output which involves more than just the on/off ratio captured by the duty cycle.