3/26/2014 Active Physics 11.8: Gauss's Law

Gauss's Law

Questions from active physics

Simulation of question 1

 Simulation of question 2

Simulation of question 3

Simulation of question 4

3/24/2014 Electric Flux & Active Physics 11.7 Flux

Flux as a Function of Surface Angle

Measuring angles of the surface that electric flux(nail) going through.   

Recorded angles of the surface that include different number of flux(nail).  Use symmetry to determine the angles corresponding to negative flux after measure the angles of positive flux.   

 Plot of the flux as a function of radians.  The curve fit as cosine function.  

Active Physics 11.7 Flux

Question 1: Flux Into or Out of an Oval

Change the shapes of oval does affect the flux.  

The flux does not changes when move the center of the oval anywhere surrounds the charge.  

The flux=0 when the oval does not surrounds the change.  

The flux increase as magnitude of charge increases.  The sign of flux changes when the sign of charge change.  

Question 2: Electric Flux with Two Charges

Change the shape of the ring does not change the flux.  Change the position of the center of the ring surround charges does not change the flux; flux changed only if the number of charge inside the ring change.  The net charge inside the ring is the sum of total charges.

Question 3: First way to determine electric flux
The flux is doubled(tripled) when the electric charge inside the oval is double(triple).  The net electric flux  is directly proportional to the net charge inside the oval.
Equation: Φ = 4πkQin 

Question 4: Second way to determine electric flux
The net electric flux is directly proportional to the net number of electric field lines leaving or entering the oval.
Equation: Φ = Number of electric field lines times (1.89E10+4 N/C)

3/19/2014 E-Field Excel Spreadsheet & ActivePhysics 11.4 & Electric Field Hockey

E-Field Excel Spreadsheet

Using the excel spreadsheet to calculate the magnitude of electric field at each distances of 0.5~10.0 cm(left side of excel).  Calculate the electric field at each point of #1, #2, #3, and #4(right side of excel).  

Using the excel spreadsheet to calculate the net electric field at the point P(left side of excel) and point P'(right side of excel).  

Electric Field Hockey

ActivePhysics 11.4

 Positive charge have outward electric field 

 Negative charge have inward electric field 

3/17/2014 Electric Force Law Video Analysis Activity

Electric Force Law Video Analysis Activity

Measured experiment data and graph of electrical force vs separation distance and its curve fit.  The curve of the graph showed that when the force between two ball increases as distance decreases.  

The equation that we use to calculated value of F(electrical).  The variable "X" is the distance moved of the hanging ball from its equilibrium point.    

Free body diagram of the ball being suspended at an angle and derivation of the equations we used to determine F(electrical).  The calculation on the bottom part is using experimental data to calculate the charge of those identical balls(q=4.19E-8 C).   

3/12/2014 Diesel Cycle

Diesel Cycle

Steps for solving the cycle problem: First, find the pressure, volume, and temperature at each point.  Second, find the internal energy at each point. Third, using the internal energy at each point to calculate the heat and work during each path.  Finally, using the data to solve for change of entropy on each path.  At the first time I was solving this question, I use the wrong equation which is use for solve monatomic gas to solving this one.  I also use the wrong value for Cv and Cp.  

Second time I just using the right equations for diatomic gas and plug in with right value for Cv and Cp then I got the right answer.  

STEM Presentation & Poster Competition

3/10/2014 Course Work: Analyzing the Cycle, The Carnot Engine Cycle, ActivePhysics-8.7 Heat Capacity

Analyzing the Cycle

Completed cycle of heat engine in pressure vs volume graph.  During the part A of the cycle is work done by the gas and part C is work done on the gas.  In part A, the hot water transfers just enough heat energy to the gas so that it expands at constant pressure and does work on its surroundings.  In part C, the cold water just enough cooled the gas so that it compress at constant pressure and does work done by its surroundings.  

The Carnot Engine Cycle 

Pressure vs volume graph of a completed Carnot engine cycle.  Base on the data point to find the internal energy at each point.  After calculated the internal energy, find the Q and W.  

ActivePhysics 

8.7 Heat Capacity

Using the numbers we have obtained to estimate the constant pressure molar specific heat capacity of this ideal gas.

Using the data we record to calculate the constant pressure molar heat capacity of the ideal gas.  

Calculating the constant-pressure molar heat capacity of an Ideal Gas.  

3/5/2014 Experiment: The Fire Syringe

The Fire Syringe

Using the syringe to determine inside temperature of the syringe changes when compress the air inside the syringe.  

Recorded experiment data and calculating final temperature inside the syringe.  Base on the final temperature we calculated, the tissue paper in the fire syringe will burns when the plunger is pushed down rapidly.  

Since we observed the smoke inside the syringe right after the plunger is pushed down rapidly, the final temperature inside the syringe increases.  

ActivPhysics- Thermodynamics

8.4 State Variables and Ideal Gas Law

Answers of problem 1~6.

3/3/2014 Experiment: Volume vs Temperature

Volume vs Temperature 

 We are using the flask that connects with a plunger and temperature pro to measure the changes of volume when temperature changed.  Base on the theorem of thermal expansion state that when a object is heated, its particles begin moving more and thus usually maintain a greater average separation; therefore, volume of air increases when temperature increased.   

Recorded experiment data and graph of temperature vs volume.  The reason that the pressure of the air remains constant even if the volume of the air in the system changes is the air inside the system will balance with atmospheric pressure automatically if the system without any external force.  

There is linear relationship between temperature and volume.  Volume is directly proportional to temperature.  

2/26/2014 Experiment: Thermal Expansion & Latent Heat of Vaporization & Pressure vs Volume and Pressure vs Temperature

Thermal Expansion

1) After the ring been heated, area of the hole expanded.  

2) Different material has different thermal expansion.  

Using steam generator to heat up the metal pipe and using experiment data to determine material of the metal pipe.  

Graphs of temperature vs time and angle vs time.  

  Determine the relationship between angular displacement of pulley and linear displacement; then plug it into the equation of alpha to calculate thermal expansion rate.  

Proving the equation of alpha with uncertainty of measured diameter and recalculate the thermal expansion rate.  

Physical meaning of thermal expansion:  
When a object is heated, its particles begin moving more and thus usually maintain a greater average separation.

Latent Heat of Vaporization

Ideal graph of temperature vs time.  

Using immersion heater to heat up 200 ml of water till it boiled.  

Graph of temperature vs time.  

Recorded experiment data and calculating the latent heat of vaporization.  

Calculating standard deviation of latent heat base on each group's experimental data.  

Pressure vs Volume and Pressure vs Temperature

Graph: Pressure vs Volume

Equations: Relationship between weight and area

Experimental graph of pressure vs volume by using pressure detector to measure pressure changed over volume.  

Graph of pressure vs temperature.  

Physical meaning of pressure vs temperature:  

When the speed of a gas's molecules increase, the gas molecules hit their container more often.  The more frequently the gas impacts the container walls, the higher the pressure.  So, as temperature increase, the pressure also increases.  If the gas cools, the impacts are less frequent and the pressure decrease.  

Conclusion:  
In thermal expansion, temperature increase, the volume of object also increases.  In latent heat of vaporization, the latent heat we measured(1400000J/kg) is way off then the actual data(2256000J/kg).  The possible error in our experiment is the way we measure the volume of water.  We should use scale instead graduated cylinder to measure the mass of water.  Because scale is more accurate than graduated cylinder.  In pressure vs volume/temperature, pressure and volume has inverse proportion relationship.  On the other, pressure is directly proportional to temperature.