Nov 12, 2005

We started with a discussion of what we know about electricity. We simulated the flow of electricity using steel balls. When a rolling ball strikes a line of balls the line of balls don't all move. Instead one ball at the other end of the line bounces off. The same electron entering one end of a wire doesn't fly out the other end. Rather the electrons bump each other and a different electron flies out at the other end.

Next we used Multi meters to check the voltage of several different sizes of batteries. Some of the batteries were 9 volts and others were 1.5 volts. When we checked them a few of the batteries had the voltage written on the battery others had almost no voltage. We decided that the batteries with little or no voltage were old and used up. We talked about why AA, C and D batteries are all 1.5 volts. We decided that they all have the same power but the bigger batteries may last longer.

Next we made batteries. We took a piece of paper towel and got it wet with salty water. Then we put a piece of metal on both sides of the paper. We used the multi-meters to check and see if any voltage was created. If we used the same metal on both sides the voltage was 0. If we used different metals the voltages ranged from .1 volts to .6 volts. We used many different metal objects like paper clips, copper tubes, lead weights, door knobs, pop cans etc.

After our break we used a computer applet to experiment with electrical circuits. We used the applet to make circuits with one battery, one resistor, and one ammeter. We recorded the voltage, resistance and current on a worksheet. First we set voltage = resistance ___ current and tried different operations + - x / to see what would make the two sides of the equation equal. After we found the rule, we solved the equation for resistance and current. Then we made a circuit with 2 resistors and found that the same equations worked if we added the resistances together and treated them as one total resistor.