What Is a Circuit? Simple Explanation for Kids

What is electricity?

Everything around you is made of tiny particles called atoms. Inside atoms are even tinier particles called electrons. When electrons move along a path, that flow is called electric current, or electricity.

A battery works like a pump. It pushes electricity out one side and pulls it back in the other. A circuit gives the electricity a path to follow so it can do something useful along the way, like light an LED, ring a buzzer or spin a motor.

The parts of a circuit

Every working circuit has three main parts, and many have a fourth:

Power source: where the energy comes from, like a battery. At home, wall outlets are power sources too, and only grown-ups should ever work with those.
Conductor: the path electricity travels along. Wires, metal and salty play dough are all conductors.
Load: the part that uses the energy to do a job, like an LED that makes light, a buzzer that makes sound or a motor that makes motion.
Switch (optional): a part that opens and closes the loop so you can turn the load on and off.

Memory tip: "circuit" sounds a lot like "circle." To be a complete circuit, electricity has to be able to travel all the way around and back to where it started.

Open and closed circuits

A closed circuit is a complete loop, so electricity flows and the LED lights. An open circuit has a gap somewhere in the loop, so the electricity stops and everything in that loop turns off.

Diagram comparing a closed circuit, where the LED lights, with an open circuit, where a gap in the dough breaks the loop, the LED is dark and a warning sign marks the gap — Tap to enlarge. Closed: the loop is complete and the LED lights. Open: the dough is split, so the loop is broken and the LED goes dark.

Tap to enlarge. Closed: the loop is complete and the LED lights. Open: the dough is split, so the loop is broken and the LED goes dark.

A light switch on your wall works exactly this way. Flip it off and it opens a gap in the circuit. Flip it on and it closes the gap so the light comes on.

Try it with dough

Build a simple circuit with play dough

The fastest way to understand a circuit is to build one. All you need is a battery holder, some conductive dough and an LED.

You need

Battery holder with 4 AA batteries
Conductive (salty) play dough
1 LED

Steps

Roll two balls of conductive dough, each about the size of a golf ball, and press them into short logs.
Set the two pieces on the table about a finger-width apart. They must not touch.
Push the red wire from the battery holder into one piece and the black wire into the other.
Gently spread the LED legs apart. Push the long leg into the dough with the red wire and the short leg into the dough with the black wire.
Switch the battery holder on and watch the LED light up.

A battery holder wired to a ball of blue dough and a ball of red dough, with an LED glowing across the gap between them — Two pieces of conductive dough, a gap between them, and an LED bridging the gap.

What happens

The LED glows because you made a complete loop. Electricity flows out of the battery holder through the red wire, into the first piece of dough, through the LED, into the second piece of dough and back through the black wire.

Not working?

Make sure the two pieces of dough are not touching, the long LED leg is on the red-wire side, and the batteries are fresh. Still dark? Flip the LED around. If the dough pieces touch, you have made a short circuit.

Series and parallel circuits

Once one LED works, try adding a second. There are two ways to connect them.

Series circuit: the parts sit on one single path, one after another. They share the energy, so each LED glows dimmer, and if one part breaks the whole loop goes dark. To build one, set three pieces of dough in a ring with a gap between each. Put the red and black wires in two pieces that sit next to each other, then put an LED across each of the other two gaps.
Parallel circuit: each part gets its own path back to the battery, so the LEDs glow brighter, and if one stops working the others keep going. To build one, roll two long cylinders of dough and set them side by side with a gap. Put the red wire in one and the black wire in the other, then bridge the gap with as many LEDs as you like.

Diagram comparing a series circuit, three pieces of dough in a ring with two dim LEDs on one path, with a parallel circuit, two long dough cylinders with three bright LEDs each on its own path — Tap to enlarge. Series: electricity goes through one LED and then the next. Parallel: each LED bridges the same two cylinders of dough, so each gets its own path.

Tap to enlarge. Series: electricity goes through one LED and then the next. Parallel: each LED bridges the same two cylinders of dough, so each gets its own path.

The outlets and lights in your home are wired in parallel. That is why one burned-out bulb does not turn off every light in the house.

Key words

Circuit: A complete loop that electricity flows around.
Electricity: Energy carried by moving electric charges, such as electrons.
Power source: Where the energy in a circuit comes from, like a battery.
Conductor: A material electricity can flow through easily, like metal or salty dough.
Insulator: A material that blocks electricity, like plastic, rubber or sugar dough.
Load: The part of a circuit that uses the energy, like an LED, buzzer or motor.
Open circuit: A circuit with a gap in the loop, so no electricity flows.
Closed circuit: A complete loop, so electricity flows.

For teachers

Our diagrams show electricity flowing from the red (positive) side around to the black (negative) side. This is conventional current, the direction used in most circuit diagrams and textbooks. The electrons themselves actually drift the other way, from negative to positive. Both describe the same loop.

This activity supports NGSS 4-PS3-2: energy can be transferred from place to place by electric currents. Ask students to predict what will happen before they close each gap, then explain the result using the words power source, conductor and load. Find free lesson plans on our education page.

Watch: what is a circuit?

Circuit questions

What are the 3 main parts of a circuit?

A power source (like a battery), a conductor that carries the electricity (like wires or conductive dough) and a load that uses the energy (like an LED, buzzer or motor). Many circuits also include a switch to turn the load on and off.

What is the difference between an open and a closed circuit?

A closed circuit is a complete loop, so electricity flows and the load works. An open circuit has a gap or break somewhere, so the electricity stops and the load turns off. Switches work by opening and closing a circuit.

Why does a circuit have to be a loop?

Electricity only flows when it has a complete path out of the power source and back again. If the path is broken anywhere, the flow stops everywhere in that loop. That is why one gap in the dough turns the LED off.

What is a simple circuit?

A simple circuit has one power source, one path and one load, like a battery holder, two pieces of conductive dough and a single LED. It is the first circuit most kids build and the starting point for everything else.

Can play dough conduct electricity?

Yes. Play dough made with salt conducts electricity, because dissolved salt lets electric charge move through the dough. Dough made with sugar instead of salt does not conduct, so it works as an insulator. Learn more in Conductors and Insulators.

Is it safe for kids to build circuits?

Building circuits with play dough is a safe, hands-on way to learn, because it runs on four AA batteries (6 volts). It is designed for ages 8 and up, and younger kids can join in with an adult. Never experiment with wall outlets, extension cords or household wiring, which carry far more power.

Printable guide: Circuits Explained (PDF)

Next, try a project

Build the Circuit Project A free step-by-step project with printable instructions.

What Is a Circuit?