Circuit With a Switch: A Practical Guide to Basic Electrical Circuits

Parts and Materials

• 6‑volt battery
• Low‑voltage incandescent lamp (e.g., Radio Shack #272‑1130 or equivalent)
• Long lengths of 22‑gauge or larger wire
• Standard on‑off toggle switch (available at any hardware store)

Why Use a Household Switch?

Standard toggle switches are inexpensive, durable, and safe for battery‑powered experiments. Avoid dimmers; the simple on‑off action best illustrates basic circuit behavior.

Cross‑References

Lessons In Electric Circuits, Volume 1, Chapter 1: "Basic Concepts of Electricity"

Learning Objectives

• Understand how a switch controls current flow.
• Use an ohmmeter to verify switch operation.

Schematic Diagram

Illustration

Instructions

Construct a single‑battery, single‑switch, single‑lamp circuit as shown. Long wires emphasize how a switch can control current regardless of circuit length.

1. Connect the battery terminals to the lamp and switch as indicated in the schematic.
2. Use a voltmeter to measure:
   • Battery voltage (across the terminals)
   • Switch voltage (across the screw terminals)
   • Lamp voltage (with the switch in both open and closed positions)
3. Observe that when the switch is off (open), the lamp immediately turns off—just as if a wire were disconnected.
4. Note that any break in the circuit, at any point, causes the lamp to de‑energize.

Related Worksheets

• Switches Worksheet