Introduction

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## A Simple Electric Circuit

Consider the simple electric circuit shown below that consists of a single circuit element and a single battery. The circuit element is indicated to have resistance (most do), and the electric current flows throughout the circuit as indicated by the arrows. The battery has a "plus pole" and a "minus pole." The current flow is caused by the battery voltage, and current always flows out of the positive terminal and into the negative terminal.

In this simple circuit, there is only one path that the current can flow. Notice that current to flow in a loop as indicated, current must flow through every circuit element, including the battery. Furthermore, the current must have the same value everywhere in this circuit, since there is only one path the current can take.

### Check it Out!

Electric current is a bit abstract - it sometimes helps to form analogies using more familiar quantities. Take for example, the flow of air through a soda straw.

Find a soda straw, and blow air through it. The resulting flow of air in the straw is analogous to the flow of electric charge in a circuit.