Resistores em paralelo (Rp)
Rp = (R1·R2)/(R1+R2).
Rp (Ω)
—
Two resistors in parallel: product-over-sum
When you have exactly two resistors in parallel, the general formula collapses to something handy: R = (R₁·R₂) / (R₁ + R₂). That comes straight out of 1/R = 1/R₁ + 1/R₂. Whatever you get, it will be smaller than the smaller of the two resistors. Both see the same voltage, and the current splits inversely with resistance (I ∝ 1/R). A couple of examples: 100 Ω || 100 Ω works out to (100·100)/200 = 50 Ω, and 1 kΩ || 2.2 kΩ lands around 687.5 Ω.
Applications
It shows up when you need to split dissipated power across several parts, build in some redundancy on power-supply paths, or hit a non-standard value that the E12/E24 series doesn't offer. Parallel sense resistors for current measurement in switching regulators are another common case.
FAQ
Why is the parallel total smaller than the smallest resistor? Every extra path you give the current pulls the overall resistance down.
How does the current divide? It goes inversely with each resistor, so the smaller R carries more current at the same voltage.
How do I choose the wattage? Each resistor dissipates P = V²/R. The smaller ones burn more power, so rate them accordingly.
Related Tools
Rent Adjustment Calculator
Compute annual rent adjustment by IGP-M or IPCA accumulated in the last 12 months (manually configurable).
Pregnancy Calculator
Compute estimated due date (EDD), gestational age and trimester from the last menstrual period (LMP).
Fertile Period Calculator
Compute fertile window and ovulation day from the first day of the last cycle and the average cycle length.