CSLB C-10 Electrical ContractorElectrical Theory and CalculationsEasy
A 120V circuit powers a 1500W electric heater. If the circuit has a total resistance of 9.6 ohms, what is the approximate current flowing through the heater?
- A12.5 amps
- B8 amps
- C10 amps
- D15 amps
Show answer & explanationAnswer & explanation
Correct answer: A. 12.5 amps
To find the current (I) when power (P) and voltage (V) are known, use the formula I = P / V. So, I = 1500W / 120V = 12.5 amps. The resistance value is extra information not needed for this calculation.
Why the other options are wrong
- B. This would be the current if the power was 960W or the voltage was higher.
- C. This is too low, indicating a calculation error or incorrect formula use.
- D. This would be the current if the power was 1800W, or voltage was lower.
Power Formula (Current)
The formula I = P / V calculates the current in a circuit when the power consumed and the voltage supplied are known.
- Current (I) is measured in amperes (A).
- Power (P) is measured in watts (W).
- Voltage (V) is measured in volts (V).
- This is a rearrangement of the basic power formula P = V * I.
Memory trick: Power over Voltage gives Current's flow.