# Kirchhoff's Current Law

Kirchhoff’s Current Law says the currents flowing into a node add up to zero.

## What is the big zig-zag symbol?

The $\sum$ symbol is the Greek letter capital Sigma. In mathematical notation it indicates the *summation* operation. It is used to sum up a number of related quantities. The expression

$i_1 + i_2 + i_3 + i_4 + i_5 = 0$

can be written compactly as,

$\displaystyle \sum_{n=1}^{n=5} i_n = 0$

It is understood that the index, $n$, runs from lower limit $n=1$ to upper limit $n=5$, stepping by $1$.

Created by Willy McAllister.