Here are some explorations to do and things to think about as we start the section on sources of electrical energy.

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• In a flashlight there are two batteries, stacked end-to-end, with the bump-end of one against the indented end of the next. This way of connecting batteries is called "putting the batteries in series." Compare the behavior of the light bulb when connected to one, two, or three batteries this way (you could also try four or more batteries, if you don't care what happens to the light bulb).
  

• Compare the behavior of the motor when connected to one, two, or three batteries in series.
• In your kit you will find "light-emitting diode" (picture at right). Compare its behavior with one battery and two batteries in series (don't connect it to three batteries. It is easy to burn out). This is an example of a "nonlinear" device: it doesn't do anything if the voltage is not high enough -- there is no current flowing at all.
• A different way to connect several batteries is to put them in parallel, as shown in this diagram. Predict how this system will behave, and then make it. Is there any use for this combination?

  Yes    No

  
  
• When different metals touch and are in a salty or acidic solution, a kind of battery results, which causes a current to flow from one metal to the other and then through the liquid. This was first discovered by Alessandro Volta, who was studying a frog's leg that was hanging from an iron support when he touched it with a silver knife -- it made the leg twitch. Can you give other examples of things happening when you have different metals in a solution? (Note that your mouth contains a solution of stuff, and contains some excellent detectors of unusual behavior).

Check the box when you are done:  
Next:Making a battery