In a parallel connection the reciprocals of the resistances add up; the equivalent resistance is smaller than the smallest of them.
Symbols
R
equivalent resistance
[Ω]
R1,R2
component resistances
[Ω]
Where it comes from
In a parallel connection the current has several paths, so it flows more easily — the equivalent resistance is smaller than the smallest resistor. For two: R=R1+R2R1R2.
When to use it
Elements connected “side by side” (the same voltage across each).
Example
Two resistors of 6 Ω and 3 Ω are connected in parallel. Calculate the equivalent resistance.