Making a Bulb Light Up
- Physics
- Ages 8–11 · Grades 3–5
- Hands-on experiment
What you’ll find out
- Electricity flows only around a complete loop, called a circuit.
- A switch works by opening and closing a gap in the loop.
- Conductors, such as metals, let electricity through; insulators, such as plastic, do not.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
A complete loop
A bulb needs electricity to light up. Electricity can only flow around a complete loop, and we call the loop a circuit. Join a wire from the battery to the bulb, and another from the bulb back to the battery. The bulb lights! Take one wire off and it goes out, because the loop is broken. A switch breaks the loop when you turn it off.
What lets electricity through
Leave a gap in the loop and try filling it. A metal nail or a key makes the bulb light. Metal lets electricity through, so we call it a conductor. A plastic ruler or a rubber band leaves the bulb dark. They do not let electricity through, so we call them insulators. Wires have metal inside and plastic outside, to keep the electricity in.
Curriculum links: NGSS 4-PS3-2