FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsMedium
A series circuit is powered by a 24-volt battery and contains three resistors. The voltmeter readings across R1 and R2 are 8 volts and 10 volts, respectively. Using Kirchhoff's Voltage Law, what is the voltage drop across R3?
- A2 volts
- B14 volts
- C6 volts
- D18 volts
Show answer & explanationAnswer & explanation
Correct answer: C. 6 volts
Kirchhoff's Voltage Law states that the sum of voltage drops in a series circuit equals the source voltage. 24V - 8V - 10V = 6V, so R3 must drop 6 volts to satisfy the law.
Why the other options are wrong
- A. Incorrect subtraction; does not balance the loop equation.
- B. This value would only be correct if drops were added rather than subtracted from source.
- D. This exceeds the remaining voltage available in the loop.
Kirchhoff's Voltage Law (KVL)
The sum of all voltage drops around a closed series loop equals the applied source voltage.
- Applies to any closed loop circuit
- Sum of drops = source EMF
- Used to find unknown voltage drops in series circuits
Memory trick: What goes up (source) must come down (drops) — it all balances.