Series and Parallel Circuits
Every real circuit is built from just two ways of connecting parts: one path (series) or many paths (parallel). Once you can see which is which and collapse the mix step by step, you can read almost any circuit on Earth.
The big idea
Imagine electric current as water flowing through pipes, pushed by a pump (the battery). If there is only one pipe, all the water must go through every part in turn: that is a series connection. If the pipe splits into several pipes that rejoin later, the water shares itself between them: that is a parallel connection. These two patterns, mixed together, make every gadget you own.
What you will be able to do after this lesson
- Tell a series connection from a parallel one just by looking.
- Add resistances in series: $R_{total} = R_1 + R_2 + \dots$
- Combine two resistors in parallel with the product-over-sum rule, and use the equal-resistor shortcut.
- Explain why adding parallel branches makes the total resistance go down.
- Find every current and voltage in a mixed circuit by collapsing it step by step.
- Use Kirchhoff's two plain-language rules (current in = current out; drops around a loop add up to the source).
- Connect an ammeter and a voltmeter correctly, and know why swapping them is dangerous.