Playful Circuits

Objectives

• Students will be able to identify the following components of an electric circuit: energy source, switch, resistance.

• Students will build series and parallel circuits.

• Students will create a personalized electric-circuit craft project.

Materials

• see individual activities for materials.

Background

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. The break in this path may be deliberate, as in a switch.

• 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)

 

Resistance is a measure of the opposition to current flow in an electrical circuit, and is measured in ohms, symbolized by the Greek letter omega (Ω).

All materials resist current flow to some degree. They fall into one of two broad categories:

• Conductors: Materials that offer very little resistance where electrons can move easily. Examples: silver, copper, gold and aluminum.
• Insulators: Materials that present high resistance and restrict the flow of electrons. Examples: Rubber, paper, glass, wood and plastic.

Vocabulary

Electron – a component of an atom, negatively charged

Circuit – a path along which electric current (electrons) can flow. For a continuous flow of electrons, there must be an unbroken path from the energy source (a battery, generator, or wall socket) through the device that uses the power, and back to the energy source

Resistance – something in a circuit which slows the flow of electrons.  Sometimes the resistance does useful work; motors and light bulbs fill the role of resistance in a circuit.  Sometimes resistance is added to slow the flow of electrons so that the electric devices are not overwhelmed with current.

Short Circuit – a circuit with very little resistance.  For example, you create a short circuit when you connect the positive and negative ends of a battery together directly with wire. The flow of electrons (current) in a short circuit is very fast and can produce a lot of heat.

Series Circuit – a circuit in which there is a single path through all the devices that use power.  In a series circuit, the current passing through each electrical device is the same.  The devices share the circuit’s energy.  Three bulbs linked in series will be dimmer than a single bulb in the same circuit.

Parallel Circuit – a circuit in which there are multiple paths.  Each device connected in parallel receives the full energy of the source.  Three bulbs linked in parallel will each be as bright as a single bulb in the same circuit. However, a battery-powered circuit with three bulbs in parallel will use up the battery faster than a single bulb attached to the same battery.

Switch – a method of breaking and re-making the circuit to control the flow of electrons.

Conductor – an item or material that allows electrons to flow through it easily is a conductor.

Insulator – An item or material that does not easily allow electrons to flow through it is an insulator.  Note that a material which is an insulator in a low-voltage circuit will become a conductor at a higher voltage.  So a person won’t conduct enough current to be part of a squishy circuit, but will conduct plenty of current if they come in contact with a wall outlet.

Voltage – a measurement of the energy supplied per unit charge (this quantity is called electric potential) by an energy source.  The coin cell batteries in this workshop supply 3V of potential.  An AA battery supplies 1.5V.

L.E.D. – Light Emitting Diodes function as tiny light bulbs.  They light up due to the movement of electrons through a semiconductor material.  A full explanation can be found at: How Stuff Works

TEACHER TIP: 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.  The energy that passes through an LED is usually regulated by adding resistance to the circuit, which is why we make sure that playdough is always part of a squishy circuit.

Other Resources

BC Hydro | Exploring Simple Circuits

For more ideas and tips: Exploratorium | Tinkering Studio

“Making” projects (electrical and non-electrical) |Book | The Art of Tinkering by Karen Wilkinson and Mike Petrich

How Stuff Works | How Light Emitting Diodes Work