I love any activity that allows students to observe and experience the basic concepts being discussed. This is just such an activity. Rather than telling students the difference between series and parallel circuits, they see for themselves by building examples of each. By looking at the brightness of the bulbs and listening to or observing the speed of the motor, they can then answer questions about how the two types of circuits differ. They will also be able to see the advantages and disadvantages of each. (N.B. The advantages I come up with for series circuits are the convenience of turning on multiple things at once, and series circuits use fewer resources.)
For this activity, you will need some basic supplies, and these are best ordered ahead of time. You will need batteries, battery holders, bulbs, bulb holders, small motors, and test leads. Most teacher-oriented science supply companies have these. Check the voltages of the motors and bulbs. It is possible to burn out the motors and bulbs with too much voltage. Alternately, it is possible to run a current through a high-voltage bulb and complete a circuit without having the filament glow. I have had good luck with 4.5-volt bulbs.
This activity comes with directions written into the lab. I have included a photo of one of the circuits showing the materials we have used. I have also included the rubric I use with this activity. All files are available as PDF or editable Word files.
In this activity, students are asked to draw schematics of their circuits. The lab includes the standard symbols for each of the parts (battery, motor, bulb, and test lead). Your students will enjoy seeing a schematic of a complex circuit. I have included an image of a complex circuit, but many are available online. I have also included a file of basic schematic symbols. Be sure to show students that the wires in are schematic are all shown with right-angle turns, even if that is not how they are arranged in the device depicted.