HOLT Electricians Practice Exam

What is the nameplate current of a 1 horsepower, 120-volt motor?

1. 10 amperes

2. 12 amperes

3. 14 amperes

4. 16 amperes

The correct answer is: 14 amperes

To determine the nameplate current of a 1 horsepower, 120-volt motor, it is essential to convert horsepower to watts because electrical power is often expressed in watts. One horsepower is equivalent to approximately 746 watts. Using the formula for electrical power (P = V x I), where P is power in watts, V is voltage, and I is current in amperes, we can rearrange this to find the current: I = P / V. Substituting the values for a 1 horsepower motor at 120 volts gives the following calculation: 1 HP = 746 watts Voltage = 120 volts Thus: I = 746 watts / 120 volts = 6.2167 amperes. However, this calculated current is for a typical efficiency scenario. In practice, electric motors have efficiency ratings that can range, and starting currents can be significantly higher. Additionally, many electricians utilize a standard rule for estimating current draw in single-phase motors, which can lead to higher rounded values being considered. These estimates and factors often suggest adjusted nominal values for simplicity and safety in installation, which can vary slightly depending on the starting and running conditions. Therefore, a common range noted for a 1 horsepower motor at such voltage might