What is the percent duty cycle for an electrical current that flows for 30 seconds and is off for 10 seconds?

• A. 50%
• B. 66%
• C. 75%
• D. 80%

Answer: (C)

To determine the percent duty cycle, it is essential to understand the concept of duty cycle in the context of electrical currents, particularly in therapeutic modalities used in athletic training.

The percent duty cycle represents the ratio of the time that the electrical current is on (active) to the total time of the cycle, expressed as a percentage. The formula used to calculate the duty cycle is:

[ \text{Duty Cycle (%)} = \left( \frac{\text{On Time}}{\text{On Time} + \text{Off Time}} \right) \times 100 ]

In this specific example, the current flows for 30 seconds (on time) and is off for 10 seconds (off time).

First, we calculate the total time of one cycle:

[ \text{Total Time} = \text{On Time} + \text{Off Time} = 30 \text{ seconds} + 10 \text{ seconds} = 40 \text{ seconds} ]

Next, we find the duty cycle:

[ \text{Duty Cycle (%)} = \left( \frac{30 \text{ seconds}}{40 \text{ seconds}} \right) \times 100 =