Computers consist of electronic circuits, which use electricity to receive, transfer, process and display information. This unit develops the basic principles of circuit operation, beginning with a coin battery and light emitting diode (LED). Students are challenged to make the LED light up, and then explore the operation of this simple circuit using a circulating penguin toy as a model for explaining concepts of source, load, conductor, insulator, voltage and current. They explore which combinations of LEDs will or will not light up together, and test a variety of materials to determine which are insulators and which are conductors. Following a “Switch Hunt” for switches in the environment, This investigation becomes the basis for constructing and understanding switches, and adding them to circuits. After drawing their circuits, they learn the standard language of schematic diagrams, which scientists and engineers use to represent circuits.