Elevator Mechanic Practice Exam

What is the Law of Power in electrical terms?

1. E=I/R

2. P=VxI

3. P=VI cosθ

4. P=ExI

The correct answer is: P=ExI

The Law of Power in electrical terms is commonly expressed in the form of P=VI, where P represents power, V is voltage, and I is current. This relationship illustrates how power can be calculated as the product of voltage and current in a circuit. The correct answer involves more specific scenarios of power calculation, particularly involving the angle of phase difference in alternating current (AC) systems, hence P=VI cosθ. This formula accounts for the power factor (cosθ), which is crucial in real-world applications where currents and voltages may not be perfectly in phase due to inductive or capacitive components. The option you selected, while intuitively appealing, doesn’t accurately reflect the commonly accepted formulas for calculating electrical power in either DC or AC systems. Thus, recognizing the relevance of phase angle in many AC systems emphasizes the importance of the correct expression for power.