More Power

     We had a lovely fiesta this past Wednesday! Instead of taking a typical quiz, we were given the materials shown in the above picture and asked to construct a circuit which lit the light bulbs as dimly as possible. In order to do this, we simply connected the two batteries in parallel and hooked them up to the two light bulbs which were connected in series. 

 

     There was also an experiment performed on Wednesday which involved a resistive coil that would heat a known mass of water when voltage was applied to it. We were given the mass of the water, the dimensions of the coil, and the applied voltage. Our goal was to determine the change in temperature of the water with our given information after a period of ten minutes had elapsed. We first determined the resistance of the coil and the current flowing through it. Because other groups had used a different value of resistivity and calculated a different current, we used these two values to come up with an uncertainty for the current. We then determined the power, the energy put into the water, and finally the change in temperature with uncertainty. The actual change in temperature was 2.5 degrees Celsius, but we calculated a change of 2 + or - .49 degrees Celsius. We went through the same process with an initial voltage of 9 volts instead of 4.5 volts. Those calculations are seen in the upper portion of the whiteboard. Doubling the voltage did not double the change in temperature. My intuition told me it would not because doubling the voltage, doubles the current, which increases the power by a factor of four.

      These are some hotdogs with 120 volts passing through them. The longer, thinner one cooked more quickly because it had more resistance than the shorter one with a greater cross sectional area. Some LEDs were placed into the hot dog to show that the further the leads of the LED were placed from each other, the greater the electric potential would be between the two leads. This was proven by observing that the LED with its leads positioned furthest apart burned out almost immediately.