A pulsed electrical stimulation has 2 ms on time and 8 ms off time. What is the duty cycle?

• A. 20%
• B. 80%
• C. 2%
• D. 50%

Answer: (A)

Duty cycle is the proportion of time the electrical stimulus is on within one cycle. Here, the on-time is 2 ms and the off-time is 8 ms, so one cycle lasts 10 ms. The duty cycle = on-time / (on-time + off-time) = 2 ms / 10 ms = 0.20, or 20%.

This means the current is active for one-fifth of each cycle and off for the remaining four-fifths. A higher duty cycle (e.g., 80%) would require longer on-time relative to off-time (8 ms on, 2 ms off), while a very small percentage (2%) would imply a very short on-time (0.2 ms). A 50% duty cycle would have equal on and off times (for example, 5 ms on and 5 ms off).