4/9 week 7 day 1 Current, Voltage and resistance

At the beginning of the class, the professor showed us a video and let us use a bulb, a bettery and a piece of wire to make the bulb light. And what we made is in the photo. 

In this photo, we sketch three different arrangements in which the bulb lights at the left and two arrangements in which the bulb doesn't light.

in this photo, we describe the reasons why the two arrangements in thich the bulb doesn't light.

In this photo, we use two same battary to make the bulb lights twice a bright.

Then the professor use a rubber bar rubbing by animal skin and put the bar on the ball, we find that the two pieces of sheetmetal seperate.

in this photo, we guess that when we put a battery on the ball, there is nothing would happen.

in this photo, we explain that why the bulb light. the reason is that there is a circle between the battery and the bulb and the charges can equilibrium.

in this photo, we list two rthings that the waterfall. 

in this photo, we use V and I to find the unit of Power. and we use a example to find P

Then in this photo, we make a circle to let the bulb light and read the Current. and we read the current is 124mA. and it is positive. Then when we reverse the leads going into and out of the ammerter, we find that the neddle goes opposition side, we read is 130mA.

We predict that model C is correct, but the experiment shows that the direction of the current will be as show and it will be the same in both wires.

In this photo,we figure out that what will influence the current. 

In this photo, we begin to learn the Ohm's law.  and we draw the graph of the realtionship between current and voltage

Then the professor uses the equipments and logger pro to draw the graph with Current and Volt.

in this photo, there are two graphs, one is V-I, another is I-V

in this photo, we sue the way of calculationg to find the constant number R and find the unit of R.

in this photo, we use the equipment in the first photo, to calculate the resistivity of different samples.
in the second photo, we use the same Nickel wings, but the length is different , and we find the longer length has the larger resisitivity.

in this photo, we use the same Nickel material, but the diameter, we find that the larger diameter, or area has the smaller resistivity.

 and we also find the different material has different resistivity. So we say that R=pL/A

Conclusion:

Today in class, we analyzed the relationship between current, voltage, and resistance by Joules Law, for which volts= current*resistance (V=IR). We also look at current flow and its various properties, such as direction and what affects the rate of flow. After experiments, we understand how a circuit works and how to insure a current flow through it. When the path is perpendicular to the Electric Field there is no work done on the E-Field because the angle is 90 degrees between the two vectors. We also looked into Ohm's Law, which allowed us to relate various properties. The proportionality of current and voltage are related to resistors found using Ohm's law.