1. Batteries: the Chemistry
Batteries use a chemical reaction to generate electricity.

2. Circuits: One Loop or Two?
Circuits can be run in parallel or series.
In a series circuit, each component is connected, one after the other, in a single loop. In the circuit on the left, the bulb, motor, and switches are connected one after another in a single loop. Electricity flows through each part in turn. If one part in the loop goes out, so will all the others.
In a parallel circuit, the electrical current is split into two or more pathways or loops. The parts in the two loop circuit on the right are connected in parallel. If both switches are on in the circuit on the right, both light bulbs light up. If one switch is turned off, that light bulb will go out, but the other will stay lit.