Resistors, parallel line notation?

[ZedCar]

I was looking at an answer regarding resistors, and saw the notation;

R = R1 + R//
where
1/R// = 1/R2 + 1/R3

I was wondering what the two parallel lines after the R indicate?

Thanks.

 

[gneill]

I was looking at an answer regarding resistors, and saw the notation;

R = R1 + R//
where
1/R// = 1/R2 + 1/R3

I was wondering what the two parallel lines after the R indicate?

Thanks.

It's just a clever choice of variable name. The $||$ is meant to convey the meaning "parallel", as it does in mathematical notation.

Parallel resistors are combined by the formula indicated, that is,

$$R_{||} = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n}}$$