Coulomb's law experiment lab report conclusion

Lab 1

Electric Fields and Electric Potential

Submitted by:

Name 21 March 2016

Abstract: This lab focuses on Newton’s second law and Coulomb’s law. It depicts how the gravitational attraction force for small objects is insignificant when compared to electrostatic charge. The lab uses an internet application to demonstrate how equal and opposite charges on pith balls create a repulsion force that deflects the pith balls from the neutral position. A cat is used to charge a rod that charges the pith balls.

This experiment demonstrates how derive the electrostatic constant, the mass of a pith ball and the tension created on the string attached to the pith balls. Everything is done within a controlled environment to produce the most accurate results

�1

Objectives:……………….……………………………………………………………………….. 2 Procedure: ...................................................................................................................................... 3 Experimental Data:......................................................................................................................... 5 Results:............................................................................................................................................ 6 Discussion and Analysis: ................................................................................................................ 7 Conclusion: ..................................................................................................................................... 8

Objective: The purpose of this experiment is to explore electrostatic charge and coulomb’s law, using some pith balls, Schrödinger’s cat, a charging rod, a grounding rod, and some basic measurement tools. This experiment will allow the performer to calculate the electric force, the electrostatic constant and various other values.

�2

Procedure: ��� ��� ��� Part 1:

Charge the charging rod by rubbing in briskly on the cat. The cat shouldn’t move if it does there is a problem. Once the charge level reaches maximum, for this cat it’s an arbitrary 120. Move the charging rod to the pith balls. They will begin to repel each other with an equal but opposite charge. Use the protractor to measure angle between the neutral line and the left pith ball and call that “θ,” and use the scale to measure the distance from the left pith ball to the right pith ball, and call that “r.” Once these are values are measured use the formula below to determine the electric force, “Felect,” weight, “W,” tension, “T,” given charge, “Qg,”, and calculated charge, “Qc.” The gravitational attraction force or “Fgrav,” is considered negligible and will not be calculated yet.

�3

���

Part 2: Similar to part 1 but only charge the rod to 100. This time

measure r and L in the above free body diagram. This will be used to calculate the mass of the pith balls and the tension force. All of the above equations apply.

Part 3: Similar to both parts but this time charge the rod to 80. Use the

same free body diagram above, and the same equations. This time the purpose is to determine a value for the electrostatic constant, “k.”

�4

Experimental Data:

Part 1 :

Part 2 :

Part 3 :

Qg 6.168e-9C θ 6° n 3.855e10 electrons

Felec t 5.0865e-5 N

z 2.05e12

Qc 6.168e-9C r 8.2cm W 4.905e-4N Fgra v 2.4e-17N T 4.93e-4N

mb 0.05g

Qg 4.692e-9C θm 5° Felect 5.0865e-5N T 4.94e-4N

l 39.2cm r 6.8cm Fgrav 2.4e-17N

mbg 0.05g mbc 0.0502g θc 4.96°

Qg 3.357-9C θ 4°

ke 8.99e9Nm2/C2 r 5.4cm

kc 8.875e9Nm2/C2 T 4.92e-4N

�5

�6

Discussion and Analysis: Part 1:

This first experiment gave the expected results. It was calculated that 3.855 × 1010 electrons are in one pith ball and the other has a deficit of that many electrons. The gravitational attraction between the two pith balls was shown to be negligible and approximately 2.4 × 10−17𝑁 and thus confirmed the assumption that it could be left out of the free body diagram. It was shown that the electric force was significantly more impactful then the gravitational attraction force, using the equation that solved for “z” determined that the electric force was 2.05 × 1012times larger than the gravitational attraction force. The percent error was 0% since the calculated charge and the given charge were exactly the same. This is probably due to the fact that the equations used to calculate these values are also used as part of the program to determine the given value.

Part 2: This experiment was fairly accurate producing results with less

than half a percent deviation. The equations and the values measured were able to produce a mass within .02mg of the actual mass. Possible error could be derived from the estimation of the scale measurements. It can be difficult to determine accurately a value between two whole numbers on the scale. All calculated values were put in the tables in the experimental data section of the lab book, and calculated in the results section.

Part 3: This experiment produced the most error again this is probably

due to the lack of accuracy of the scale. Also since many values are squared at the end this can also help exaggerate the error of the protractor and scale.

�7

Conclusion: The stated objectives were met, all values were calculated within an acceptable amount of error. The free body diagram was same for every set up so only one was drawn since all values can be derived from the same equations. This lab teaches an abstract application to Coulomb’s law as well as how to manipulate the equations for Newton’s second law and derive missing variables using the given values.

�8

�9

�10