Modeling Open and Closed Circuits
Inside the ping-pong shaped energy ball is a battery, light, and buzzer. These parts are connected to each other by an electrical conducting wire, which means electrons can flow through the wire. Current electricity is when electrons flow through a material.
On each end of the conducting wire is a metal strip which extends through the ball. These metal strips are called electrodes. One electrode is attached to the negative terminal (end) of the battery and the other electrode leads back to the positive terminal of the battery.
FYI: The symbol for the battery in the circuit diagram is a long and a short line. The short line represents the battery’s negative terminal and the long line represents the battery’s positive terminal.
Even though there is a battery present and the battery is connected to the light and buzzer, there is no flow of electrons because there is a gap between the metal strips.
For electrons to flow through an electric circuit, a continuous unbroken path must start from one battery terminal and end at the opposite battery terminal. In other words, an electric current (flow of electrons) needs a continuous conductive path, which is called a closed circuit.
The diagram of the hand holding the energy ball is an example of a closed circuit. Touching the electrodes on the energy ball with the index finger and thumb bridges the gap between the electrodes. Notice that electrons from the energy ball are flowing through the hand.
Is it safe to hold the energy ball? YES!
The energy ball produces a very small amount of electric current.
FYI: Dry skin is not conductive. Moisten dry skin with lotion so it will conduct the current from the ball.
The following video provides more information about the energy ball. It also show students forming complete (closed) circuits in various ways, such as holding hands so that the electrical current travels from the energy ball through each person in the circle, then back to the energy ball.
Any break in the circle creates an open circuit, thus the ball and buzzer will not work.
