The NASA SCIence Files™
Circuits
Safety Check
  • Do not play with electricity.
  • Do not place objects on top of electrical cords or wires becasue the wires may become damaged.
  • When using electrical devices, follow all instructions.
  • When you remove a plug from a wall outlet, use the plug; do not pull on the cord.
P.U. thinking of a circuit

When you flip a light switch on and off, you are closing and opening a circuit. A circuit is the path that electricity follows. For electrons to travel (creating an electric current), the circuit must be closed. When you flip the light switch off, you are opening the circuit and the lights turn off. When you flip the switch on, the circuit it closed and the lights come on.

Let's take a closer look at circuits . . .

Here is a circuit diagram that the tree house detectives gave me. What do you think this circuit does? Here are common circuit parts along with how the part is drawn in a circuit diagram:

battery Voltage source
conductor Conductor
load Load
switch Switch


Did You Know?
  • You can use math to figure out exactly what is happening at any point inside of a circuit.
  • Math can help us learn just how much electricity is required by each of the different loads in a circuit.
  • Math is cool!
So, have you got all this circuit stuff figured out yet? There is one more thing I think you should know: the difference between series and parallel circuits.  Take your pick!

diagram of series circuit Series Circuits
A series circuit allows electrons to follow only one path. All of the electricity follows path #1. The loads in a series circuit must share the available voltage. In other words, each load in a series circuit will use up some portion of the voltage, leaving less for the next load in the circuit. This means that the light, heat, or sound given off by the device will be reduced.

diagram of parallel circuit Parallel Circuits
In parallel circuits, the electric current can follow more than one path to return to the source, so it splits up among all the available paths. In the diagram, some current follows path #1, while the remainder splits off from #1 and follows path #2. Across all the paths in a parallel circuit the voltage is the same, so each device will produce its full output.