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💡 What Makes a Bulb Light Up

Peek inside a light bulb and meet the tiny glowing wire called the filament. Learn how electricity flowing through it heats it white-hot to make light — and heat.

lessons

~15 min

to learn

🔬 Science

subject

Ages 6–12

level

Start the course →

What you’ll learn

Inside a Light BulbName the parts of a light bulb, especially the filament, and describe what each part does.A light bulb's glow comes from the filament, a thin coiled wire, often tungsten, inside a glass bulb. The glass protects the filament, and the metal base joins the bulb into a circuit. Coiling lets a long wire fit into a tiny space.
Why the Bulb GlowsUnderstand that a filament resists the current, heats up, and glows to give light and heat.The thin filament resists the flowing electricity, and squeezing through makes it heat up. When it gets hot enough, it glows white-hot and shines out light. A glowing bulb makes both light and heat, which is why old bulbs feel warm.
From Electricity to LightFollow the steps by which a bulb changes electrical energy into light and heat.Electricity enters the base, reaches the filament, and makes it resist and heat up until it glows, turning electrical energy into light and heat. Modern LED bulbs make light differently and stay cool, saving energy, but the filament bulb clearly shows how electricity becomes light.

Questions this course answers

What is the thin, glowing wire inside a bulb called?

The filament is the thin, coiled wire inside a bulb that glows to make light.

What is the job of the metal base at the bottom of a bulb?

The metal base connects the bulb into the circuit so electricity can flow into the filament.

Why does the filament heat up when electricity flows through it?

The thin filament resists the electricity, and squeezing through makes it heat up.

Besides light, what else does a glowing bulb give off?

A glowing filament makes light and heat, which is why an old bulb feels warm.

In a bulb, electrical energy is changed mainly into which kinds of energy?

The bulb changes electrical energy into light energy and heat energy.

How are modern LED bulbs different from filament bulbs?

LED bulbs make light in a different way, staying cool and turning more electricity into light, so they save energy.

Grounded in trusted sources

BBC Bitesize
Britannica Kids
The Physics Classroom
Khan Academy

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