Chapter 7, Problem 9STP

To determine

To calculate: The number of times an electric motor will rotate in one hour.

Answer to Problem 9STP

The number of times the electric motor will rotate in one hour is $\underset{\_}{180,000}$ .

Explanation of Solution

Given:

No. of times the motor rotates per second when alternating current is $60\text{ Hz}$ = $60$

New alternating current source = $50\text{ Hz}$

Calculation:

  $\begin{array}{l}\text{Number of times motor rotates per second at 60 Hz = 60}\\ \text{Number of times motor rotates per second at 1 Hz = }\frac{60}{60}=1\\ \text{Number of times motor rotates per second at 50 Hz = 50}\times \text{1 = 50}\\ \text{Number of times motor rotates per hour at 50 Hz = 50}\times \text{3600 = 180000}\end{array}$

Conclusion:

The number of times the electric motor will rotate in one hour is $\underset{\_}{180,000}$ .