Understand it in 60 seconds · Components
The resistor
Like partly closing a water valve, a resistor limits current. Protect an LED, use Ohm’s law and see where the electrical energy goes.
Beginner · published 8 October 2026
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What you will understand
- Like partly closing a water valve, a resistor limits the current: voltage is the pressure, current the flow.
- Ohm’s law, I = V/R: at the same voltage, double the resistance and the current is halved.
- Charges do not disappear in a resistor: the current is the same on both sides, and electrical energy becomes heat.
- Protect an LED: from 5 V, about 2 V across the LED and 3 V across 330 Ω, so about 9 mA. Without the resistor, too much current can destroy it.
- About 27 mW turn into heat in that resistor: a 0.25 W part covers it with margin.
Inside the lesson
The cheat sheet
Every equation on one page, with the circuit drawn. Export it to PDF to keep it.
The animated presentation
The idea step by step, with the currents flowing in the circuit. Press Present (F5) to play it.
Your own copy
It opens as a Circuit Notebook project: change the values, reuse the circuit in your report.
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Analog
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The voltage divider in 60 seconds: two resistors share the voltage, Vout = Vin·R2/(R1+R2), and a potentiometer turns a song down before the amplifier.
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Components
The diode
The diode in 60 seconds: a one-way valve for current that opens at about 0.7 V, protects a board from a reversed battery and turns AC into DC in a bridge.
