**“The algebraic sum of all the currents entering any node is equal to zero”**

This law represents a **mathematical statement** of the fact that **charge** cannot **accumulate** at a **node**. A **node** is not a** circuit element**, and it certainly cannot **store**, **destroy**, or** generate charge**. Hence, the **currents** must sum to** zero**. A **hydraulic analogy** is sometimes useful here:

for example, consider three **water pipes** joined in the **shape** of a **Y**. We define three “**currents**” as flowing into each of the **three pipes**. If we** insist** that water is always flowing, then obviously we cannot have **three positive water currents**, or the **pipes** would **burst**. This is a **result** of our defining **currents** independent of the **direction** that water is actually **flowing**.

Therefore, the value of either one or two of the **currents** as defined must be **negative**.

A **compact expression** for **Kirchhoff’s current law** is