Wired for Sound

Sound is made by vibrations. An electrical current can flow through a closed circuit. A switch is a device used to open or close an electrical circuit.

Australian Curriculum links

  • Science > Physical Sciences > Year 6 > ACSSU097

You'll need

Try this

  1. Wrap a piece of wire around one leg of the peg, leaving about 3 cm of wire sticking out to one side.
  2. Repeat this on the other leg of the peg. The end of the second piece of wire should be sticking out to the other side. The wires shouldn’t touch when the peg’s legs aren’t squeezed. The wires should touch when the peg’s legs are squeezed.
  3. Connect the four parts of the electrical circuit by:
    • Snapping the battery holder onto the battery.
    • Connecting the black wire of the battery holder to the black wire of the buzzer.
    • Connecting the red wire from the battery holder to the wire on one leg of the peg.
    • Connecting the red wire from the buzzer to the wire on the other leg of the peg.
  4. Squeeze the peg’s legs. Observe what happens.

What's happening?

Squeezing the legs of the peg makes the copper wires touch, which closes the electric circuit. A closed electric circuit is needed for electrical current to flow. The battery supplies electrical power to the circuit. The electricity flowing in the circuit causes vibrations inside the buzzer. These vibrations make the sound you hear when the peg is squeezed.

This electric circuit is composed of a battery, an electric buzzer and wires. The wires are made of copper which is a good conductor of electricity. The copper wires allow a flow of electrons to move through the circuit and this is called electrical current. Electrical current is measured in amperes (A) and it is a measure of the number of electrons passing through a conductor. In this circuit, the battery provides the voltage. Voltage is the potential energy that drives the current through the circuit and it is measured in volts (V).

In this circuit, the wires on the legs of the peg act as a switch to open and close the circuit. When the legs of the peg are squeezed, the wires on the opposite legs touch each other. This closes the circuit, allows electrons to move through the circuit and makes the buzzer sound. The sound happens because, as electricity passes through the buzzer, it causes the buzzer to vibrate. When the legs of the peg aren’t squeezed, the wires on the separate legs don’t touch each other. This means the circuit is open, so the electrons can’t move through the circuit, including the buzzer, so the buzzer doesn’t sound.

Real world links

Electric eels have organs that contain around 6,000 specialized cells called electrocytes that store power like tiny batteries. When electric eels feel threatened or are attacking prey, the electrocytes discharge simultaneously, producing a burst of at least 600 volts. This is two and half times the voltage of a standard Australian wall socket! The electrical burst stuns prey and dissuades predators.