# Battery, Switch, and Load

Part of the Electricity Merit Badge Digital Resource Guide: [Introduction & Overview](https://merit-badge.university/merit-badges/electricity/guide/index.md)

*10. Hands-On Projects*

> **10a.** Connect a buzzer, bell, or light with a battery. Have a key or switch in the line.

This is the simplest complete electrical system you can build: a source, a path, a control, and a load. Even though it is basic, it teaches one of the most important truths in electricity: current only flows when the path is complete.

## The Four Essential Parts

Your circuit needs:

- **Battery:** the power source.
- **Wires:** the path for current.
- **Switch or key:** the control that opens or closes the path.
- **Load:** the buzzer, bell, or light that uses the energy.

If any one of those parts is missing or not connected correctly, the circuit will not work.

## How to Think About the Build

Connect one battery terminal to the switch. Connect the switch to the load. Connect the load back to the other battery terminal. That creates a loop.

When the switch is open, the loop is broken and the load stays off. When the switch is closed, current flows and the light, bell, or buzzer activates.

![Simple battery, switch, and light circuit shown with the switch open and closed to illustrate when current flows](https://ik.imagekit.io/doulacoop/tr:w-800/mbu-assets/merit-badges/electricity/guide/basic-circuit-loop-with-switch?v=48d7f47f)

**Build and test sequence** — A simple way to show your counselor what is happening

- [ ] **Lay out the parts** so you can see the full path.
- [ ] **Connect the loop** from battery to switch to load and back to the battery.
- [ ] **Test with the switch open** to show that nothing happens.
- [ ] **Close the switch** to show the load working.
- [ ] **Explain the current path** out loud while you demonstrate.

> **Safety First!**
>
> Use low-voltage batteries and components designed for classroom or hobby use. Do not connect household lamps or wall-current devices directly to a battery project.

> **Tip**
>
> If the circuit does not work, check the easiest things first: battery orientation, loose wire ends, switch position, and whether the bulb or buzzer is compatible with the battery voltage.

Video: [How To Make a Simple Electric Circuit | Working Model School Science Project — School Science Project Ideas](https://www.youtube.com/watch?v=oDUAvaXsK1g)

This option is a perfect warm-up for [Req 10f — Series vs. Parallel Circuits](https://merit-badge.university/merit-badges/electricity/guide/req10f/), where you take the same basic idea and compare two different wiring arrangements.

---

- Previous: [Choose Your Circuit Projects](https://merit-badge.university/merit-badges/electricity/guide/req10/index.md)
- Next: [Simple Electric Motor](https://merit-badge.university/merit-badges/electricity/guide/req10b/index.md)