How Do Resistors Work?

This blog post on resistors is an excerpt from Level A of our Intro to Robotics  program. Level A covers building circuits, using a Raspberry Pi, and writing common code commands in Python. It contains 350 pages with 18 lessons and 45 projects and activities. Sample lessons and a full scope and sequence for Level A can be found here.

 

In its simplest form, a resistor provides electrical resistance: it limits the flow of the electrons through the circuit. Think of it as what happens to the density of traffic when the road is temporarily taken down to one lane and then reopened after an accident. The entire freeway is slowed down drastically by needing to move down to one lane. Similarly, when using a resistor, the flow of electrons is lessened by the resistor. Because the resistor’s job is simply to limit how quickly the electrons are flowing through the circuit as a whole, a resistor can be placed anywhere in the sequence (series) of components. From anywhere along the circuit, the resistor will slow the flow of electrons.

Diagram of how resistors work using a car caught in traffic

Resistors are useful for a few reasons. First, allowing electricity to flow from the positive charge to the negative charge without anything to stop it, causes a big safety risk known as a short circuit. The resistor moderates the flow of electrons, so the current doesn’t move too quickly and cause damage to the breadboard, wires, battery, etc. The second reason to use a resistor is to slow the current flow to a component. Components like LED’s, fans, light bulbs, etc. are designed to function with a certain amount of electrical current. Too little and they won’t work, too much and you can damage or destroy the component.

 

Using Resistors to Build Circuits

Different size (value) resistors can be used for different projects. For example, an LED has maximum voltage and current limits. Most batteries will provide far more current than the LED can handle, so you would want to use an appropriate resistor with a battery and LED to moderate the flow of electrons and keep the LED operating safely. You will learn more about how to calculate the amount of resistance needed for a component and battery in Lesson A-3 when we teach you to use Ohm's Law when designing electronics projects.

Resistors are not polarized so there’s no danger of using them backwards. When a component is polarized, it means electricity must flow in one direction and out another. Resistors can be used in series (sequence) or in parallel where multiple resistors are receiving electricity simultaneously.

Simple breadboard circuit with resistors and switch

 

This blog post on resistors is an excerpt from Level A of our Intro to Robotics  program. Level A covers building circuits, using a Raspberry Pi, and writing common code commands in Python. It contains 350 pages with 18 lessons and 45 projects and activities. Sample lessons and a full scope and sequence for Level A can be found here.

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