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Build a Circuit

In this activity students will explore the flow of electrons and build a complete electrical circuit.

A complete 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 no longer has power. 

In order to use electric current to power our lights, computers, or hairdryers, we need a complete circuit.


  • Describe the parts of a complete circuit.

  • Explain the path of electron flow through a complete circuit.


  • Per Class or Group:
    3V Coin Cell Batteries (or D-cell batteries )
    strips of tinfoil (or alligator clips)
    scissors or wire cutters
    LED’s (or a string of holiday lights)
    binder clips

    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

  • How do I know if my circuit is complete?
  • Does the direction of the flow of electrons matter?
  • How can I break the circuit?

What To Do

  1. Mount batteries on pieces of cardboard with the tape. Connect strips of tinfoil (or wire) to the positive and negative terminals being careful that they don’t touch. Mark the positive and negative side on the cardboard.
  2. If using Christmas lights, cut each light from the string leaving about 3cm of striped wire on each end.
  3. Mount lights on pieces of cardboard with the tape, being careful to leave some of the wire exposed. If using LEDs put strips of tinfoil under the legs and secure with tape. Mark the positive and negative sides on the cardboard. (Tip: to test which side is positive and which is negative test the bulb directly on a battery.
  4. Try to light up the lightbulb. Explore connecting the circuit in different ways.
  5. Make a switch by placing two binder clips on opposite ends of a piece of cardboard. Place a strip of tinfoil under one binder clip being careful not to touch the other.
  6. Explore adding a switch to the circuit.


  • Once you have built circuits with batteries and mini-lights, you can add in other electronic components like switches or buzzers.
  • Have students add multiple components to their circuit. Check out Lighting Lightbulbs (linked below) for an explanation of different types of circuits.
  • Try to build a device that runs on current electricity like our Burglar Alarm or Steady Hand Game activities (linked below).

Other Resources

BC Hydro | Exploring Simple Circuits
BC Hydro | Exploring Series and Parallel Circuits
BC Hydro | Electrical Safety

How Stuff Works | How Light Emitting Diodes Work