FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsHard
A circuit consists of a 10-ohm resistor (R1) connected in series with a parallel combination of two 20-ohm resistors (R2 and R3). This network is connected to a 40-volt battery. What is the total current supplied by the battery?
- A8 amps
- B4 amps
- C1 amp
- D2 amps
Show answer & explanationAnswer & explanation
Correct answer: D. 2 amps
The parallel combination of R2 and R3 (both 20 ohms) equals 10 ohms. Adding this to R1 in series gives a total resistance of 20 ohms. Using Ohm's Law, I = E/R = 40V/20Ω = 2 amps.
Why the other options are wrong
- A. This value assumes an incorrect total resistance of only 5 ohms.
- B. This value results from ignoring the series resistor R1.
- C. This would result from doubling the total resistance incorrectly.
Series-Parallel Combined Circuit
A circuit containing both series and parallel resistor combinations, requiring stepwise reduction to find total resistance.
- Reduce parallel sections to equivalent resistance first
- Add series resistances to the parallel equivalent
- Apply Ohm's Law to the total resistance for total current
Memory trick: Combine like puzzle pieces — parallel first, then add the series piece.