⚡ Electronics Lab · Ages 9+

Ohm's Law LED Lab

Slide the battery and the resistor. Watch how much current flows and how bright the LED glows — but be careful, too much current makes it pop! 💥

The circuit

V = I × R

Voltage = Current × Resistance

I = V ÷ R R = V ÷ I V = I × R

Cover the letter you want to find in the triangle — the rest shows the sum! 🔺

The yellow sparks are the current flowing. They speed up when more current flows.

Current meter

20mA

0203040+

Bright — just right! 🌟

Build your circuit 🔧

🔋 Battery voltage 9.0 V

🟫 Resistor 330 Ω

💡 LED colour needs 2.0 V

Why do we need a resistor? 🤔

An LED is greedy — if you connect it straight to a battery, it grabs way too much current and burns out in a flash. The resistor is like a narrow straw: it slows the current down to a safe sip.

Ohm's Law tells us exactly how much current flows:

Current = ( Battery − LED ) ÷ Resistance

A bigger resistor → less current → dimmer (but safer). A smaller resistor → more current → brighter… until it's too much. 💥

Safe current for a regular 5 mm LED

Current	What happens
under 1 mA	Too little — the LED stays dark.
1 – 20 mA	The happy zone. Glows nicely. Around 15–20 mA is nice and bright.
20 – 30 mA	Careful! Very bright and running hot. It won't last long.
over 30 mA	Too much! The LED overheats and burns out.

Tip for makers: aim for about 20 mA. Tap the green button above and the lab will pick a safe resistor for your battery and LED.