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Paper Circuits

The materials in this activity encourage students to build and explore the basic principles of electric circuits. Students make circuits with LEDs, conductive copper tape, and 3V “coin” batteries. The circuits can be incorporated into greeting cards or art projects

A circuit is a continuous path through which electricity travels. A complete electric circuit is an uninterrupted path for electrons to flow from an energy source (i.e. battery or household power), through a device and back to the source. If we break that path, the flow of electrons stops, and we no longer get energy from our circuit, and the device (in this case, light bulbs) no longer has power.

In a parallel circuit, all loads are connected in parallel to one another, forming junction points where the current can split and combine.
In a series circuit, all loads, like light bulbs, are connected end-to-end, forming a single path for the current to flow.

Parallel Circuit (top)

Series Circuit (bottom)

Objectives

Students will build series and parallel circuits.

Materials

For each Participant:
50 cm adhesive copper tape, 6 mm width
one piece of paper about 10 cm square
one 3V coin battery, size 2032 or CR1220
one or two LEDs
one binder clip
adhesive tape
needle-nose pliers
coloured paper and art supplies for making a card

CAUTION: Coin cell batteries are extremely dangerous if swallowed. This activity should be done under adult supervision and coin cell batteries should never be left where young children can come across them.

Key Questions

What are the essential parts of a circuit?
What is a complete circuit? What is a "short circuit"?
How does a switch function?
What is a circuit in series?
What is a circuit in parallel?

What To Do

Remind students of the essential parts of a circuit: there must be an energy source and a path for the current to follow through the resistance. The circuit must form a circular path from the energy source (battery) through the resistance and back to the source.
Explain that the path in this circuit will be made of copper tape.
Have students draw a square path on the paper to represent the circuit, noting where the light will be and where the battery will be.
Check the path for completeness before giving students the copper tape.
Students use the tape to cover the path they have drawn, leaving a space for the LED bulb and for the battery.
Demonstrate that the coin battery has a positive and a negative side. Show students that the long lead of the LED must connect to the positive side of the battery and the short end must connect to the negative side.
Students can now use regular adhesive tape to attach their LED to their circuit.
Finally, students should fold the paper so that one end of the circuit connects to the positive side of the battery and one end to the negative side. The binder clip holds the battery in place so that the bulb stays on. These photos show the finished product.

Once the circuit is functional, students can create a card. The students can make their own designs or you can offer some suggestions. Imagine something that includes a light – it could be a car headlight, a candle on a cake, the eye of a bird or an animal, a light in a house window or even a star in the sky. Draw the design on coloured paper and make a hole for the LED bulb to poke through.

Attach the paper circuit behind the artwork to complete your card. The photos above show the front and back of a very simple card.
Older or more experienced builders may want to use two LED bulbs. These usually must be wired in parallel. If you put two in series there is typically not enough power to light both. Teacher Tip: If you use two LEDs of different colours, sometimes only one LED will light (the one with the lowest resistance). Two LEDs of the same colour work well. LEDs are directional; they create light only when current flows through them in one direction. It’s also worth knowing that too much voltage will destroy the LED.