CalcElfCalcElf › 36 V with 6 Ω and 12 Ω: series vs parallel
36 V with 6 Ω and 12 Ω: series vs parallel
A 36 V supply is connected to two resistors, R₁ = 6 Ω and R₂ = 12 Ω. What is the main current when they are connected in series, and when they are connected in parallel?
Answer
Series total resistance 18 Ω; series current 2 A; parallel total resistance 4 Ω; parallel current 9 A
Step-by-step
- 6 + 12 = 18Series resistances add: R = R₁ + R₂
- 36 ÷ 18 = 2Ohm's law I = U / R
- 1 ÷ (1/6 + 1/12) = 4Parallel resistances add reciprocally: 1/R = 1/R₁ + 1/R₂
- 36 ÷ 4 = 9Ohm's law I = U / R (main current)
Why it works
Series resistances add up; parallel resistances combine through their reciprocals and give a total smaller than either one. The main current is then the supply voltage divided by that total resistance.
Common mistakes
- Adding 6 Ω and 12 Ω for the parallel connection.
- Dividing by the individual resistances instead of the total resistance.
Related
circuit-two-resistors-series-parallel circuit-series-parallel-current-6v n-phy-circuit-series-1