FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsMedium
A circuit contains three resistors of 10, 20, and 30 ohms connected in series to a battery. What is the total resistance of the circuit?
- A10 Ω
- B6.67 Ω
- C300 Ω
- D60 Ω
Show answer & explanationAnswer & explanation
Correct answer: D. 60 Ω
In a series circuit, total resistance equals the sum of all individual resistances: 10 + 20 + 30 = 60 ohms.
Why the other options are wrong
- A. This is only the smallest resistor value.
- B. This is the parallel-circuit calculation, not series.
- C. This results from multiplying instead of adding.
Series Circuit Resistance
In a series circuit, total resistance is the sum of all resistances because current has only one path to follow.
- Rt = R1+R2+R3...
- Current is the same through all components
- Voltage drops divide across resistors
- Adding resistors increases total resistance
Memory trick: Series resistors line up like train cars — just add their lengths.