3. Microwave Demos 1 Put Metal fork into microwave---nothing visible happens 2 Put CD into microwave.--- CD is burned 3 Put fire into microwave.---fire gets larger. 4 Put light into microwave.---to be lighter but the light is broken soon. 5 Put a soap into a microwave.--- Nothing happen 6 Put a purple metal ball into the microwave.---got burn and the fire changes color.
Summary:
In today’s class, we learn what is flux and Gauss’s Law. We know that flux is calculated by the number of electric field lines, and its go through the surface area. And we know how microwave works and how it can heat things up. We also learn what kind of material is able to absorb microwave and what kind of material is not able to absorb microwave.
The three dimension model of a positive charged electric field which is represented by the bulge and negative charged electric field which is represented by a dip.
The positive electric field points outward, and the direction of negative electric field is inward. When we put the two electric field together, the positive electric field tends to move to the negative charged electric field.
Extended Charge Distribution
Derive formula from integration. We divided the rod into little pieces.
ActivPhysics
Electric Fields were furthered studied using ActivPhysics. Questions 1-6 were answered in the whiteboard picture below.
In this lab, we rubbed the balloon with animal fur, then stick the balloon to the glass cabinet. by the experiment, we predicted that the balloon will stick in the glass because the balloon is charged by the animal fur with negative charge , and there is positive charge on the glass, they can be stick together.
If we peel two tape off the table and bring the non-sticky side of it toward each other, the tape will repel each other. The closer they are, the larger distance they will repel. And different side of tape to close to each other,
At the beginning of this experiment, we predicted that The relationship between force and distance r is inversely proportional.
The FBD about suspended ball.
By using LoggerPro, we find a graph that shows the relationship between electron force and distance, and find the values. In the lab, the theoretical value is 2, and our experimental value is 1.999. It is very close to it. The reason why it is not exact 2 is because we some times click the point not at the middle of the ball.
If two charges have same charge, then they will repel. If they are opposite signs, they will attract to each other.
The Van De Graff generator can charge other objects.
Professor Mason places a wig above the Van De Graff generator. the hair is sticking up. That is because the generator puts charges into the wig, then all the charges are same, they want to repel each other.
Then, Professor Mason puts a Franklin motor above the generator. then the Franklin motor immediately spins because the charge accumulated at the points. It is a conservation of momentum situation, the electrons streamed out of those points and moved the entire system.
