Wiring up a light for toy car

How to Make an Electrical Circuit

There is something magical about building a basic electrical circuit for the first time, connecting those wires, and watching the bulb light up. It’s exciting no matter how old you are, and even preschoolers can get in on the action.

Generally, the demonstration ends there. The circuit works, so it’s time to move on.

For us, making the electrical circuit is only half the fun. The next question is, how can we use it? How can we tweak it?

In this month’s post (the first for this blog!) we’ll show you how to make a simple electrical circuit to power an LED light. After learning how it works and making the bulb light up, you can also have fun using it as an accessory for a toy car.

What else will you engineer using this circuit? Will you wear it? Create a light-up bedroom decoration? The possibilities are endless.

Along the way, we’ll talk about simple electric circuits and their voltage, current, and resistance. These concepts will be helpful for understanding how the circuit works and for building future projects that we post.

Here’s everything you need to get started in minutes. If you don’t already have these supplies at home, you can probably pick them up at most local hardware stores. Or, you can order by following the product links at Amazon.

You can check out our video tutorial here and subscribe to our YouTube channel to keep up with new projects.

The boys also built a wacky hack to surprise Dad. Everything is explained below as well (but we can’t give away the surprise!)

Supplies for making an electric circuit

LED Christmas lights (you might burn one out)

9 volt battery

330 Ohm resistor (or a potato!)

Wire connectors or alligator clips

Copper wire

9 volt battery connector (optional)

Toy car or Legos to build one

Steps to build the electric circuit

Step 1: Build the car

Step 2: Wire one battery terminal to a resistor

Step 2a: Learn about electricity: voltage, current and resistance

Step 2b: How to connect the battery and resistor

Step 3: Connect the resistor to the LED

Step 4: Connect the LED to the other battery terminal

Step 5: Attach the light to the car

Step 1: Build the car

If you are using a pre-built toy car, skip to step 2. Otherwise, grab some Legos and go wild!

Step 2: Wire one battery terminal to a resistor

2a. Learn about electricity, voltage, current, and resistance

Now we get to start building the circuit.

Remember, electricity is what you get when electrons move. Electrons can only move if there is a complete path for them to flow through. This is also called a circuit.

So, why are we starting out by connecting a battery terminal to a resistor?

To answer that question, we need to explain three words: voltage, current, and resistance.

To understand these three words, it can be helpful to think about electricity as behaving like water.

Imagine that you have two buckets filled with water. Each bucket has a hole in its bottom connected to a hose. On the free end of each hose is a balloon.

One bucket is on the bottom step of a ladder, and the other is on the top step. The water in the hose connected to the bucket on the top step will be under more pressure. It will result in a larger water balloon. If we take the balloons off, water will flow out of the high pressure hose faster than the low pressure hose.

Buckets on ladders

Just like the water in the hose can be at different pressures, electricity can be at different voltages.

And just like with water, the electrical flow or “current” of of a circuit is higher when the voltage is higher.

Let’s take a look at the circuit drawn in the image below. If we create a simple circuit just connecting the battery to the LED, we’ll burn out the bulb. The LED is built for a certain amount of current. Too much current will break the bulb.

Circuit with battery and LED

Remember the resistor? A resistor lowers the current in a circuit. You can think of a resistor lowering electrical current like a hand squeezing a hose and slowing down the flow of water.
Hand squeezing hose

Resistors are made to have different resistances. Going back to our hose analogy, some resistors squeeze more tightly than others.

We used a 330 Ohm resistor in this circuit. A resistor with too much resistance can lower the current so much that the LED will not light up at all.

For a deep dive into how you can calculate the resistor value you need for different LED circuits, head over to Evil Mad Scientist’s Basics: Picking Resistors for LEDs.

And if you don’t have a resistor handy do you know what else you can use? A potato!

Or you could experiment with anything that lets electricity flow but slows down current. Since water conducts electricity, you could try a tube of toothpaste, a flowerpot with damp potting soil or any other fruits or vegetables.

2b. How to connect the battery and resistor

There are a few different ways to attach the pieces of the circuit together. The easiest approach is to attach a battery connector to the 9 volt battery and to use a wire connector to attach the connector wire to the resistor.

It is also possible to simply wind a piece of copper wire around one of the battery terminals. You can substitute alligator clips for wire connectors if you have them on hand.

Make sure never to create a direct path between the two battery terminals! The battery would drain and the wire would heat up.

This is an example of a circuit that doesn’t have enough resistance, which is called a “short circuit.”

Step 3: Connect the resistor to the LED

You can use a piece of copper wire with a connector (or alligator clip) on each end to connect the resistor to the LED.

Step 4: Connect the LED to the other battery terminal to complete the basic electrical circuit

When you attach the other battery connector wire to the LED, you’ll complete the circuit. Here’s what ours looked like.
Hands holding alligator clips, resistor, and LED to complete the battery-powered circuit

If the LED doesn’t light up, reverse which contact is connected to the resistor and battery.

Why? Current can only go through diodes (including LED “light-emitting-diodes”) in one direction. We’ll talk more about diodes another day.

Step 5: Attach the light to the car

If you’ve gotten this far, congrats! It’s time to put your circuit to use to deck out your own little set of wheels. Tape on your light circuit and you’re ready to roll!
Cars with lights

If you want to get started wiring up an even simpler light circuit with stuff you probably already have lying around the house, check out What Do We Do All Day’s Super Duper Simple Circuit Science Project.

You can also have more circuit fun by building one of Steam Powered Family’s adorable Circuit Bugs or The Homeschool Scientist’s Light-Up Circuit Maze.

To find out how you can actually light up play dough circuit projects, head over to STEAMsational’s How to Use Squishy Circuits.

For more tinkering inspiration, try browsing through our growing list of cool engineering projects.

Don’t forget to sign up for our free monthly newsletter to receive Geek Pack Hack updates along with an even wackier simple circuit project.

Please leave us a comment to let us know if you built this project and if you have suggestions for future posts.

Have fun!

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