Mechanics Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

To determine the output frequency of a generator, we can use the formula that relates the rotational speed (in revolutions per minute) to frequency (in hertz). The formula is given by:

\[ f = \frac{P \cdot N}{120} \]

Where:

- **f** is the frequency (in hertz),

- **P** is the number of poles, and

- **N** is the speed of the generator in revolutions per minute (rpm).

In this scenario, the generator is operating at 600 rpm and has 4 poles. By substituting these values into the formula, we have:

\[ f = \frac{4 \cdot 600}{120} \]

First, calculate the numerator:

\[ 4 \cdot 600 = 2400 \]

Next, divide by 120 to find the frequency:

\[ f = \frac{2400}{120} = 20 \text{ Hz} \]

This calculation shows that the output frequency of the generator is 20 Hz, confirming the correctness of the first choice. This highlights the process of understanding mechanical systems in relation to electrical output, specifically how the number of poles and the rotation speed interact to determine frequency.