CSLB C-10 Electrical ContractorElectrical Theory and CalculationsEasy
A 120-volt circuit powers a resistive heater with a current draw of 12.5 amperes. What is the power consumed by the heater?
- A150 watts
- B1500 watts
- C9.6 watts
- D15000 watts
Show answer & explanationAnswer & explanation
Correct answer: B. 1500 watts
Power (P) is calculated by multiplying voltage (V) by current (I). In this case, P = 120V * 12.5A = 1500 watts.
Why the other options are wrong
- A. This value is too low; it might result from an incorrect decimal placement or calculation error.
- C. This would be the result if current was divided by voltage, which is incorrect for power.
- D. This value is too high, indicating a potential multiplication error (e.g., by 10 or 100).
Power Formula (DC/Resistive AC)
The formula P = V * I calculates the electrical power consumed by a resistive load, where P is power in watts, V is voltage in volts, and I is current in amperes.
- Applies to DC circuits and purely resistive AC circuits.
- Power is measured in watts (W).
- Voltage is measured in volts (V).
- Current is measured in amperes (A).
Memory trick: Volts times Amps gives you Watts of Power.