Introduction: Circuit Buddies

Have you ever wondered how electricity works? Just as blood vessels carry blood throughout the body, wires in a circuit carry electric currents through various parts of an electronic system.

What is a circuit? A circuit is a path that moves electrical currents. This electricity is used to provide power for lights, and other electronic devices we enjoy on a daily basis.

This lesson teaches students the basics of how an electronic circuit works and the functionality of four simple electronic components. The capacitor, resistor, switch and diode. They will also learn the schematic symbols for the components as well.


Investigate and illustrate the fact that the flow of electricity requires a closed circuit ( a complete loop).


1 LED -



9 Volt Battery- 1 can be used for a group up to 10 students

Step 1: Gathering Supplies

1 LED -



9 Volt Battery- 1 can be used for a group up to 10 students

Step 2: Understanding the Resistor

The Resistor

The most fundamental of circuit components and symbols!A resistor "resists" the flow of electrons. You can think of a resistor as different size pipes, the bigger the pipe the easier water can flow, the smaller the pipe the harder it is. If you buy a milkshake and get a big thick straw and drink the milkshake it is easy, but if you drink the same milkshake using a small straw like a coffee stirrer it will be very hard. You will also be able to drink the milkshake must fast using the bigger straw than the smaller. The size of the resistor in our circuit limits how quickly the capacitor will drain its charge. It also protects our LED from getting too much current and getting damaged. We'll discuss that later.

Resistance is measured in Ohms the higher the value the more resistance to the flow of electrons. So the higher the resistance, the smaller the straw in our milkshake example.

Resistors on a schematic are usually represented by a few zig-zag lines, with two terminals extending outward. Schematics using international symbols may instead use a featureless rectangle, instead of the squiggles.

Step 3: Understanding the Capacitor

The Capacitor

The capacitance is the ability of a component to store an electrical charge. You can think of it as the "capacity" to store a charge. A capacitor can be thought of as a bucket of water. You can fill that bucket up with water and it will hold it as long as there are no leaks or holes in the bucket. The size of the capacitor is equivalent to the size of the bucket the bigger the bucket, the more charge/water it can hold. The Farad is the measurement of a capacitors ability to store a charge, the higher the number the more charge/energy it can store. In this project we are using a 470 micro-farad capacitor. There are two commonly used capacitor symbols. One symbol represents a polarized (usually electrolytic or tantalum) capacitor, and the other is for non-polarized caps. In each case there are two terminals, running perpendicularly into plates. The symbol with one curved plate indicates that the capacitor is polarized. The curved plate represents the cathode of the capacitor, which should be at a lower voltage than the positive, anode pin. A plus sign might also be added to the positive pin of the polarized capacitor symbol.-- Learn More

Step 4: Identify the Positives!

Time to create your circuit buddy!

Identify the longer Capacitor leg- It's the Positive! The capacitor also designates the negative side with a stripe and a - symbol on its side. Using a resistor- twist around the positive leg from behind and twisting upward- Bend the capacitor leg at the bottom to stand-

Step 5: Understanding the Diode/LED - Light Emitting Diode

A Diode

A diode is a semiconductor component that only allows the flow of electrons in one direction. Its schematic symbol looks kind of like an arrow pointing the direction that electricity can flow. It also has a vertical line at the tip of the arrow representing the blocking of flow in the reverse direction. The LED that we are using in this circuit emits light when current is flowing and is called a Light Emitting Diode. Diodes are polarized so it has a positive (anode) side and a negative (cathode) side and requires something to identify which is which. Most diodes have a longer leg to let you know which is the positive side. The LED can only handle a little bit of current and can be damaged if connected directly to the battery. Current is measured in Amperes which represents the flow of electrons. Typical diodes can handle around 10-20 milliamps of current safely. The resistors in our circuit decrease the current and protect the diode from getting damaged. Think of it like trying to drink water from a fire hose. Your stomach would burst! The resistors make it more like drinking from a garden hose instead.

Step 6: 2 Positives Make It Right

Identify the longer LED leg- It's also the positive!

Using the previous resistor wire- Twist to connect to the positive LED wire- The Resistor is the connector of the 2 positive wires/ and the flow of energy between the capacitor and the LED.

Step 7: Home Stretch

Using the second resistor wire-

Twist around the short LED wire downward.

A resistor represents a given amount of resistance in a circuit. Resistance is a measure of how the flow of electric current is opposed or "resisted."

Step 8: Make a Loop

Bend the bottom of the resistor wire to make a loop.

The loop is your switch!

A switch is a component which controls the open-ness or closed-ness of an electric circuit. They allow control over current flow in a circuit.

Step 9: Charge Them Up

Your buddy is ready to be charged.

Connect the positive legs to the positive side/ and negative legs to the negative side of the 9 Volt Battery .

Hold for 2-5 seconds!

When a battery is connected to a series resistor and capacitor, the initial current is high as the battery transports charge from one plate of the capacitor to the other.

Step 10: Understanding the Switch

The Switch

The switch is a component that controls the flow of electricity. The basic switch has 2 positions open and closed. When a switch is "open" that means that electricity cannot flow through it and is represented in the picture above. It shows that the 2 wires are not connected. When a switch is "closed" it creates a "short circuit" which can be represented with the gate part of the switch closed showing the 2 wires connected and then electricity can flow from one side to the other. The switch in our circuit is the arm of our circuit buddy that has the loop and can be touched to his leg. When the switch is closed energy flows out of the charged capacitor through the first resistor, through the LED and then through the second resistor and finally ends at the negative side of the capacitor. A circuit is complete when current can flow from the highest voltage to the lowest voltage through our loop of components. Voltage is measured in Volts and represent the electric potential or "electric pressure" that a circuit has. In our case we are charging our capacitor to 9 Volts. When you close the switch the voltage will slowly drop as the capacitor empties itself through the Resistors and LED. As the voltage drops the LED will shine less brightly until finally the voltage is too low to light the LED and your capacitor is discharged. By touching the Capacitor to the 9V battery you are filling it back up to 9V again.

Step 11: Simon Says " Touch Your Leg!"

Use the Looped arm to touch the negative leg-

When your buddy lights up- you know he has been charged and your circuit is good!

Step 12: Ready to Play!

Your buddy can be recharged as many times as you need!

An electrical circuit is a path or line through which an electrical current flows. The path may be closed (joined at both ends), making it a loop. A closed circuit makes electrical current flow possible. It may also be an open circuit where the electron flow is cut short because the path is broken. An open circuit does not allow electrical current to flow.

Step 13: Making Friends!

You can use your buddy to connect to other buddies! Watch the energy flow!

Step 14: The Science Behind the Fun

This lesson teaches students the basics of how an electronic circuit works and the functionality of four simple electronic components. The capacitor, resistor, switch and diode (actually the LED- Light emitting diode).

The students created a simple electronic circuit by twisting the component leads (wires) together in the correct order. The circuit resembled a little robot man when put together with an LED for his head. The capacitor was charged by touching it to a 9-volt battery, the capacitor held it’s charge until the switch (the resistor lead that is not connected, is the switch) was closed and the LED lit up until the capacitor was discharged.

Science is fun!

Happy Creating!

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