Discussion of the section on energy sources

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  1. Herecomparing two batteries in series to a single battery with a different voltage are two circuits. Assume that the current in each circuit is 2 Amperes. How much power is each battery producing? How much power is being delivered to the light bulb, in each case? Use a similar pair of circuits to demonstrate that any pair of batteries in series is equivalent to a single battery with a higher voltage.  
  2. Kim measured the voltage of the battery she made, and finds that it is over 2.5 V (with all four layers). So she concludes that the problem is that the battery cannot make enough current. In the analogy between electrical systems and water systems, what is the equivalent of a battery? What is the water equivalent of the battery you made, that wouldn't light a light bulb?
  3. three ways to connect two car batteries Suppose your car has a weak battery. The radio will play and the lights go on (a bit orange, perhaps), but the engine won't turn over. Using a set of jumper cables you can get the car started. The instructions say to connect the plus terminal of one battery to the plus terminal of the other battery, and then connect the car frame of one car to the car frame of the other car (this is equivalent to connecting the negative terminals, as in diagram A).

    Other ways to connect the jumper cables would be to connect plus-to-minus, minus-to-plus (diagram B), or to connect the batteries in series (by disconnecting the wire at the positive terminal of the dead battery and connecting it instead to the positive terminal of the good battery, and then connecting the negative terminal of the good battery to the positive terminal of the dead battery, as shown in diagram C). What unpleasant results would these options give?

  4. Suppose the reason that your car won't start is that the battery has been stolen and replaced with a block of wood painted to look like a battery. Now what will happen if you connect the jumper cables according to diagrams A, B, and C?

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