FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsMedium
Two resistors, 6 ohms and 3 ohms, are connected in parallel across a 12-volt battery. What is the total resistance of the combination?
- A18 Ω
- B4.5 Ω
- C2 Ω
- D9 Ω
Show answer & explanationAnswer & explanation
Correct answer: C. 2 Ω
For two resistors in parallel, Rt = (R1×R2)/(R1+R2) = (6×3)/(6+3) = 18/9 = 2 ohms.
Why the other options are wrong
- A. This is only the numerator of the formula without dividing.
- B. This is an average of the two values, not the parallel formula.
- D. This is simply the sum, which applies to series circuits.
Parallel Circuit Resistance
Total resistance in a parallel circuit is always less than the smallest individual resistor because current has multiple paths.
- Formula for two resistors: Rt=(R1×R2)/(R1+R2)
- Rt is always less than smallest branch resistance
- Voltage is same across each branch
- Current divides among branches
Memory trick: Parallel paths make it easier for current, so total resistance drops.