Here are some things to do to finish this section.

• What question did you think of that could be studied, or observation could you make that is interesting or unexpected? Send it to the Question board!

1. You can buy light bulbs intended for 115 V with a wide range of wattages -- 5 W for little nightlights up to 250 W and more for lights intended to illuminate the whole back yard. Which kind uses the most current? Which kind has the highest electrical resistance (and what is the numerical value, in Ohms)?
2. Is it safe to combine ordinary 115 V light bulbs with the materials in the kit? What would happen if we connect a 40 W light bulb from the grocery store to a battery? (Please give a quantitative discussion -- with Volts and Amps and Watts and Ohms)
3. In your kit you will find a small piece of thermal sensing sheet. It is a kind of thermometer, that is probably black at room temperature but will turn green or blue when you touch it (or if it is rather warm in the room). When you are through playing with it, let it cool back to a uniform color. Meanwhile, cut a piece of aluminum foil that is 1/2 cm wide and 10 cm long. Straight is OK, but it is more fun if it is somewhat curvy. We are going to use this as a wire. Place the thermal sensing sheet on top of the aluminum foil wire, so that the two ends of the foil stick out. Attach wires with clip ends to the battery, and then to the ends of the aluminum foil, to make the circuit diagrammed at left. Explain what happens.
   
   Notice that what we have made here is an example of the circuit (sometimes called "a short circuit"), which you were warned not to make. What's wrong with a short circuit?

This is the end of this unit. (Check this box )   The next section is about circuits