3/26 Week 5 day 2 Electric flux and dipole torque

 At the beginning of the class, the professor asked us to draw the sketch about there are two lines, one is filled with particles with positive electric, the other is negative electric. I draw the sketch looking like in the photo, the direction of the electric field is from the positvie line to negative line. And then put a negative particle into them, the particle movement orbits is forward down.

Then we learn about electric dipole, which forms with two same electric particles， but one is negative, the other is positive, the direction of the electric dipole is from negative particle to positive particle. We put electric dipole in a electric field looks like in the photo, we find the direction of forces that the two particles are different, and the directions are oppisite.

in this photo, we use the equation torque= F*r to find the torque in electric dipole. We find the two particle in electric dipole have same torque but the direction is different. and the net torque is 2 times than one of them.
and the electric moment P=2*q*a and we find that torque=P*E.

in this photo, we use another way to find the work of electric dipole. We find the work is the change of potential energy.

in this photo, we draw the direction of normal vectors of the electric diople. 

Then we use the VPython to show it

in this photo, we draw the electric field line between the positive and negative particle and we find that the direction of electric field line is always from postive particle to negative particle.

in this photo, we draw the Normal vectors to the surfaces shown in the picture.

Then we begin to learn the Flux. 

in this photo, we find the unit of flux is N*m^2/C

in this photo, we find the Flux of 4 different area in the cube, becasue the electric field lines is from left the right, so the flux of 3 and 4 is 0, and about 1 and 2 is =E*A

Conclusion:
Today in class, we first learn what is the dipole and how to find the torque of dipole . We use VPython to draw the direction of normal vectors of the electric dipole. And we build some model of Electric flux and learn how to find the flux of different surfaces.

3/24 Week 5 day1 Electric Field

at the beginning of the class, the professor asked us to change the gravity situations to electric situations. what we did is in the photo.

in this photo, we combine the equation F=k*q_1*q_2/r^2 and E=F/q to find the E= k*q_2/r^2.

in this photo, we put a proton in the 3-D coordinate system and mark the directions of electric field, we can find that all directions deviate from the proton.

in this photo, we want to find the Electric field equation. and we have 5 steps in the photo.

Then in this photo, the professor ask us to predict electric vectors located and their directions. 

in these photos, we use the codes that professor gives us and use the equation to find

Then we begin to do the exercises about electric field. in this photo, we put two opposite balls which have + and another has -. and we should find the total E of a special position. That position is on the right side. we also use the equation:E=k*q/r^2 to find it.

in this photo, we change the position that we want to know. we place it on the middle of the two electric balls and find the E_total. in this question, we should find the x and y axis 's E and add them together. 

This is another exercise we did today, we also should find the E for every part on the line to the special point. this one is a little hard because we should find their distant r.  in the second photo, we use excel to find the E total is 59715 N/C.

 in this photo, we find the position of the middle of the line and find the E_total. We find the E_x and E_y first and add them. we find that the E_x is 0 and E_y is 110210 N/C

in this photo, we use another way to find the total E of the special position. what we did is in the photo, and we calculate that E_total=60000 N/C is same as what we got about 59715 N/C.



Conclusion:
Today in class, we learn what is electric field and how to express the electric field. We learn how to draw the lines in a electric field .and use equation E=kq/r^2 to find the how strong in an electric field.

Vpython

Vpython1.py

 Vpython2.py

3/19 week4 day2 New things: Electrical Force and charge.

Today, the first experiment we did is that the professor use a balloon rub the hair and put it near the wall, predict the result. We find that the ballon and the wall are sticking together. 

Then we use tht balloon will be rubbed with a silk cloth, then we find that it sticks to the glass wall again.
The results of these show that after the balloon was rubbed, it can produce charge. and becasue of thse charge, the balloon become sticky.

Then the professor askes us to definite the charge for a 7 year-old kid, what we say is on the photo.

Then we start another experiment about Interactions of Scotch Tape Strips. In the first video, two partners peel their tape off the table and bring the non-sticky side of the tape toward your partner's strip. We find that the two tapes push each other. and larger distance means waker interaction.

In this video, we place two strips of tape on the table sticky side down and label them "B" for bottom, and press another strip of tape on top of each of the B pieces; label these strips "T" for top. Pull each pair of strips off the table. Then pull the top and bottom strips apart. We find that the two T tapes are repell and the two B tapes are also repell , but when we put one T tape and one B tape together, they stick together.

in this photo, in A and B we describe what happen in the two videos. In C,  my observations are consistent with the hypothesis that there are two types of charges.
In D, hypothesis is false, charges can be conducted by plastic.

In the left of the photo, we can calculate the angle=sin^(-1)(X2/L)
In the right of the photo, we did the exerices in the lab manual. 

in this photo, we make a sketch of a graph of F and r. and use the equation:F=A*r^B and find B=-2, A=Gm1m2. In the second photo, we did the graph in logger pro and curve it .

 in this photo,we show the force's relationship worked on q1 and q2.

 in this photo, we use the equation: F=kq1q2/r^2 to find the force worked  by p1 on p2. 

in this photo, we put q1 q 2 q3 in a xy-axis. and use  F=kq1q2/r^2 to find the force on x-asix and y-asix  on P3 by p1 and p2 

in this photo, we did an experiment usng the equipment in the photo. And we give power in it, we find that the paper is all floating.

Then we put another equipment on it, we find it will rotate。

In this photo, we want to find the relationship between F1 which worked by eletrons and F2 which worked by earth. 


Conclusion:Today in class, we did many experiments that about charges caused by electrical forces that cause an object to either attract or repel. we use Coulomb's law  to measure the electrical force which is found to be greater than gravity.

3/17 week 4 day 1 Entropy and different cycles.

today in class, we continue to learn the different cycles.

when we put it on the hot water, this equipment begins to go up and down.  but when we cool down the bottom of it and pour ice water on it, it starts to go down and up.

then we use the equation: e=1-T_c/T_h  to find its efficiency.

in this photo, we start to learn how to find the cop(coefficient of performance) and we use the cop to find the total heat we use. 

in these photos, we find the second law efficiencies of the heat engine. We should find the Actual output of enerhy desired and Maximum output of energy by reversible process.

in these two photos, we know how to find the final temperature when we know that the reversile process is also constant.

Then we compare the efficiency of carnot cycle and efficiency of reversubke process.

 in this photo, we find the Q_H by using EQUATION:W=Q_H- Q_c

then we did an experiment about bubbles. when we make bubbles by air, they will fall down. but when we use nature gas, it will go up. 

When we fire the bubbles, it burns the whole outside that we can see from the video. 



conclusion:

Today in class, we learn different cycles. the different cycles have different efficiency. The entropy of a system is measured as the amount of disorder in a system. we learn how to find the cop.we compare the efficiency of carnot cycle and efficiency of reversubke process.