Formula
Series resistance is the sum. Parallel resistance is the reciprocal of the sum of the reciprocals. A field at zero is not a short and not an open. It is an unused slot.
Rseries = R1 + R2 + …
1 / Rparallel = 1/R1 + 1/R2 + …
Two equal resistors in parallel are half of one. The voltage divider is the special case of two resistors with a voltage across the string. The Ohm’s law calculator turns the total into current and power.
Worked examples
100 Ω parallel with 100 Ω. 50 Ω.
100 Ω, 200 Ω, and 200 Ω in parallel. Conductance is 0.01 + 0.005 + 0.005 = 0.02 S, so the total is 50 Ω.
Those three in series. 500 Ω.
Reference
Five slots. Combine a longer network in groups and enter the group totals.
Questions
What is 100 Ω in parallel with 100 Ω?
50 Ω. Two equal resistors in parallel are half of one of them. The same two in series are 200 Ω.
What if a field is left at zero?
A zero is skipped. The total uses only the resistors you set above zero.
Is there a limit to how many?
The form holds five. For a longer string, combine a group, then enter that result as one of the five.
Sources
- Series sum, and the parallel conductance sum 1/R.