Circuits: Ohm's law, series and parallel, made concrete
Circuit questions test one skill: reducing a network to something simple. Noeta walks the reduction and checks each intermediate value.
What this covers
- Ohm's law V = IR
- Series and parallel resistance
- Kirchhoff's current and voltage laws
- Power dissipation
- Potential dividers
Worked example
Problem
Two resistors, 4 Ω and 6 Ω, in parallel across 12 V. Find total current.
- 1Combine resistors1/R = 1/4 + 1/6 = 5/12, so R = 2.4 Ω.
- 2Apply Ohm's lawI = V/R = 12 / 2.4.
- 3Sanity checkBranch currents 3 A + 2 A = 5 A, which matches.
Answer: 5 A
Mistakes that cost marks
- Adding parallel resistances directly instead of reciprocals.
- Forgetting that voltage is shared in series, current in parallel.
- Inverting 1/R and forgetting the final reciprocal.
Questions students ask
How do I simplify a messy circuit?
Work outward from the smallest series or parallel pair, redrawing each time. Noeta shows every redraw.
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