Day 11 Gauss Law

Gauss Law = q,enclosed/eplsillon not. We divided a couple of charges into different enclosed areas, s1, s2, s3 and drew the flux lines from each charge.

We had q1 be negative( top right), q2 and q3 are the positives one. Flux lines are going towards q1. The flux for each S (surface), s1 ,s2 ,s3 can be counted by having flux lines going out - flux lines going in. If the net result is positive then more flux went in the surface, if net result is negative more flux went out of the surface.

Another picture demonstrating flux.

Electric field only effects the normal of a surface.

Flux inside is zero in this enclosed surface.

Prof. Mason then asked us what would be the best answer if one was in a lighting storm. Our answer was to stay inside the car. It would act like a Faraday cage. 

The white board Prof. Mason picked out.

We then explained the demonstration of a lighter in the microwave. And when to use the right symbol for E calculations.

We explained the plasma and also E = sigma/Epsilon not. And when to use lambda, sigma or rho in our E calculations. We also explained what the fork did in the microwave.

We then derived the volume of a sphere and integrated in terms of  r + dr.

The white board Prof. Mason showed as example.

Our work of the same thing. dr to the powers of 2 and 3 are small so they go to zero. Only 4pir^2dr is left and is useful.

We then did some Active Physics questions that asked to find Q if the r's are different. The final answer was 1/8Q.

We set the lesser r on top and the bigger r on bottom. Did some canceling and was left with 1/8Q.

We then did use Gauss law to find E.

E = q/e0, the 4pi and e0 turns into K. E then becomes E= Kq/r^2. Similar to Coulomb's law.

Prof. Mason then pleased us by showing us what different types of things do when they are put inside a microwave. We did some prediction for some.

Fork, our prediction was the fork would cause sparks. Nothing happened.

Cd, our prediction we would see sparks. Sparks happened.

The damage to the Cd by the sparks caused by the small layer of aluminum coating on it.

Our prediction of Soap. Did  not work, but the soap would become foam.

Picture of something.

Picture of soap.

Very beautiful colors when microwaved. Melted a whole through it.

Picture.

Our predticion was that it would expand and blow up. It did not but showed a light blue glow.

We then moved on to answer some Active Physics demo and questions. The first was a slew of questions about flux.

All questions answered. Used Gauss law to find flux. Which was 40,00N/C. Flux in a smaller radius is zero. The charge is 2.39*10^4 C/m^3. Rho*V is equal to E is = 45,000 N/C.

Prof. Mason then asked us to E for a cylinder. Sa = 2pirL + 2pir^2. Lambda  = q/l.

We plugged in the numbers to the equation and got E = 4.798 N/C for the cylinder. Used q/L. The second term goes to zero since the is no perpendicular flux going through it.

For got to mention the graph we found from E(r). E field grows as the radius grows.

The E is greates when little r is equal to R. After little r becomes greater then R, E drops by 1/r^2. E(r) = qnotr/R^3.

Summary:
We found Gauss law to be useful in finding E. Flux inside different S have different flux depending on the q inside and the q outside of the S. Flux is = integral EdA. The usefulness of 4pir^2dr found for spheres. Changes in r could effect Q greater then one would think. Gauss laws is similar to Coulomb's law.
Microwaved a whole bunch of things.
Learned that little r inside of big R stores different Flux. Found the graph of E versus R.
Found the Surface area for a cylinder  Sa = 2pirL + 2pir^2. Lambda  = q/L.