Circuits and conductors
Series resistance
- where
- total resistance (Ω)
- individual resistances (Ω)
Explain this equation
Works out the total resistance of resistances connected end to end in one path. Used for strings of components and for adding conductor resistances along a route.
Rₜ is the total. R₁, R₂ and R₃ are the individual resistances. In series the same current passes through each one.
Each resistance adds its own opposition along a single path, so the totals simply add.
Sense check: 10 + 20 + 30 = 60 Ω. The total is always bigger than the largest single resistance.
Watch out: only use this where there is no branching between the parts.
In series there is one current path. Add the resistances because each contributes to the total opposition.
The total must exceed every individual positive resistance. Then find circuit current from the supply voltage and total resistance.
Enter your values to see the result.
Common mistake
Using the parallel reciprocal rule for a single path.
Limits
Resistors in series, with no branching between them.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.