# Electrical Resistance and Voltage

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## Introduction: Electrical Resistance and Voltage

The following information is a single lesson in a larger project. Find more great projects here.

Lesson Overview:

Now we'll learn about resistance and voltage!

## Step 1: Electrical Resistance

A resistor restricts or slows the flow of current through a circuit. Resistors are used to control the brightness of an LED, the volume of a buzzer, or the speed of a motor.

The electrical component called a Resistor has a resistance value measured in ohms. The colored stripes on the resistor are a code that indicates its value. The chart explains how to read the code:

1. Use the conductive pen tool to connect the two traces coming out of the battery.
2. What's changing on the battery when you do this?
3. Stuck? HINT: The red Short LED on the battery component will light up when you short the circuit.

## Step 2: Testing Resistor Values

Here is a basic circuit to get started. It has a battery for power, a Bi-LED to check the resistance and a 2Pin + Resistor.

You're going to change the value of the resistor and see if that produces any changes to the LED.

If you're trying this in the physical world, you need to put a different resistor in the circuit. In the online editor this happens automatically.

Start the simulation

1. Click on the 2Pin + Resistor module to select it.
2. Change the resistance value with the dropdown menu and see what happens!
3. Stuck? HINT: Changing the resistance value changes the brightness of the LED.

## Step 3: Photo Resistor

Standard resistors have a fixed resistance. There are also components with a variable resistance.

A photo resistor changes it's resistance based on the amount of light that shines on it.

In the physical world you could shine a light on it, in the online editor this is done by moving a slider.

1. Click on the 2-Pin + Resistor module to select it.
2. Delete the element by clicking on the trashcan in the submenu at the top left corner.
3. Add a Photo Resistor component (2Pin + LDR) and place it on the pads where the 2Pin + Resistor used to be.
4. Start the simulation.
5. Click on the Photo Resistor if it's not yet selected.
6. Change the resistance value with the slider and see what happens!
7. Stuck? HINT: The brightness of the LED changes as you move the slider.

## Step 4: Voltage

Voltage is the change in electrical potential energy between two points.

The battery is our energy source. The voltage across the battery terminals is 9 Volts.

In the first example circuit, current flows from the positive (+) end of the battery , through the LED , to the negative (-) end of the battery

1. Click on the 2-Pin + Resistor module to select it.
2. Delete the element by clicking on the trashcan in the submenu at the top left corner.
3. Add a Photo Resistor component (2Pin + LDR) and place it on the pads where the 2Pin + Resistor used to be.
4. Start the simulation.
5. Click on the Photo Resistor if it's not yet selected.
6. Change the resistance value with the slider and see what happens!
7. Stuck? HINT: The brightness of the LED changes as you move the slider.

## Step 5: Shorting a Circuit

Current takes the path of least resistance. If you draw a line which creates a path for current to flow without passing through the LED, the battery becomes “short circuited.”

The two ends of the battery are directly connected by a low resistance path, so not enough current flows through the LED to turn it on.

When the battery module is “shorted” the red indicator light comes on.

1. Use the conductive pen tool to connect the two traces coming out of the battery.
2. What's changing on the battery when you do this?
3. Stuck? HINT: The red Short LED on the battery component will light up when you short the circuit.

In the next lesson you will learn to control LEDs and use switches!

Next Lesson:Brighten Up Your Day with LEDs and Switches

## Recommendations

• ### Large Motors Class

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