Electric Field（0324）

Electric Field

In shot, charge is analogous to mass and gravity acceleration analogous to electric field. 

Steps to find electric field

Animation of electric field

Our prediction of the code

We did some practice problems in class to deepen our understandings

Electric Charge (0319)

Electric Charge

After the ball had been rubbed against the hair, it had charged, particularly positive, therefore it would stick to the glass door

Preparing for the experiment

For this experiment, we took another two pieces of tape and placed them on top of the previous ones.

Remark: The top would repel against the other top, but attracting to the other bottom. Therefore, the charges of the top and the bottom were opposite.

Our observation for the second experiment.

 

Here we have the electrical force F=A/x^2. With A=1.37*10^-5. The ratio difference is A/K= 1.37*10^-5/ 8.99*10^9 approximately about 1.52*10^-15.

b. Pick a point that has electrical force to be F_e= 0.001 and x2=0.103. We can calculate the charge of two balls q_1=q_2=( F_e/ k*x2^2)^(1/2)=(0.001/8.99*10^9*0.103^2)^1/2=3.2*10^-6C

c. Now we have the charge q_1= 0.5q_2. q_2= (F_e/2k*x2^2)^1/2=(0.001/(2*8.99*10^9*0.103^2)^1/2=2.28*10^-6C.

q_1=q_2/2=1.14*10^-6C

We calculated the charged of one onto another point charge.

This is a charge creator.

The strips are shrinking down because the charges go into the motor.

Entropy Lab Experiment (0317)

Entropy Lab Experiment

 The simple stirling engine

In the case above, we heated up the gas with hot water from the bottom.

We were calculating the max efficiency of the stirling engine. In fact, the actual efficiency of stirling engine is equivalent to the Carnot engine

Effective of the refrigerator is given by its coefficient of performance K=abs(Q_c)/abs(W)

K_carnot= T_c/ (T_h-T_c)

 The Coefficient Of Performance for an engine

Fire a bubble!!

Heat Processes (0312)

Heat Processes

The thermometric cooler convert temperature difference to electricity

Supplied power,the thermometric cooler will make different temperature

The relationship between Cv and R. The ratio is 3/2.

The relationship between Cp and R. The ratio is 5/2.

Recall that P,V, and T are not constant. Therefore, we have to use product and quotient rule to take derivatives.

We derived the formula describing the relationship between P and V, 

 P^(3/5)*V= constant at the end. 

Another derivation in adiabatic process.

Adiabatic process

Using the derived formula to find the work done.

We were introduced to how the pistons work in an engine. There are 4 steps to completing 1 engine cycle. Intake, Compression, Power and Exhaust.

A simulator of engine

In order to make enginer more powerful (not more efficient), we need more revolution of the piston moving, we need bigger volume of combustion chamber, and we need to maximize the stretch of the pressure to push all the gas molecule out.

VPython Assignment (0319)

VPython Assignment

The code:

from visual import *
sphere(pos= vector (-3,0,0),radius =1, color=color.blue)
arrow (pos=vector (-3,0,0), axis =vector (3, -3,0), color =color.red)

sphere(pos= vector (3,3,0),radius =1, color=color.blue)
arrow (pos=vector (3,3,0), axis =vector (-3, 0,0), color =color.red)

sphere(pos= vector (3,-3,0),radius =1, color=color.blue)
arrow (pos=vector (3,-3,0), axis =vector (0, 3,0), color =color.red)