Switches

Beginning students often find the terminology for switches confusing, because the words open and closed sound similar to the terminology used for doors, but do not mean quite the same thing when used in reference to a switch! In order to help avoid confusion, ask the students how they may think of these terms in a way that is consistent with their meaning in the context of an electrical switch.

One analogy to use for the switch’s function that makes sense with the schematic is a drawbridge: when the bridge is down (closed), cars may cross; when the bridge is up (open), cars cannot.

An inexpensive type of switch I use for teaching basic electricity/electronics classes is a household light switch. Available from hardware stores for very little cost, these switches are rugged and easy to connect into real circuits, large or small. For this question, you might want to let students disassemble one or two of these switches to observe how they are constructed.

This question is also a good point to start a conversation on the reliability of switches. Being that it has moving parts, what could possibly fail in a switch? How about the contacts themselves: what might happen to them over time, especially if “overloaded” with too much electrical current?

This is a difficult concept for some students to master. Make sure they all understand the nature of electrical current and the importance of continuity throughout the entire circuit. Perhaps the best way for students to master this concept is to actually build working battery-switch-lamp circuits. Remind them that their “research” of these worksheet questions is not limited to book reading. It is not only valid, but preferable for them to experiment on their own, so long as the voltages are low enough that no shock hazard exists.

One analogy to use for the switch’s function that makes sense with the schematic is a drawbridge: when the bridge is down (closed), cars may cross; when the bridge is up (open), cars cannot.