In a series connection the resistances of successive elements simply add up.
Symbols
R
equivalent resistance
[Ω]
R1,R2
component resistances
[Ω]
Where it comes from
In a series connection the current flows through all resistors one after another, so their resistances add up — the equivalent resistance is greater than each component.
When to use it
Elements connected one after another (the same current flows through each).
Example
Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. Calculate the equivalent resistance.