Lab Report 1 - Lab 1 PDF

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Lab 1...

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Noah Quanrud Lab Partner: Yung-Chuan Yang Professor Ratliff TA: Minghao Song Physics 221-L02 9/5/17 Experiment 1: Coulomb’s Law Statement of Objective The purpose of the experiment was to prove that Coulomb’s law is true, meaning that we need to show that the charge transferred is proportional between to object. In order to prove so we used a pith ball to show the proportional transfer of charge. Theory In 1785 Augustin de Coulomb investigated the attractive and repulsive forces between charged objects and came up with Coulomb’s Law. Coulomb’s Law states, “The magnitude of the electric force that a particle exerts on another is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.” The equation for the law is: F=k

q1 q2 r2

(1)

Equipment List The lab uses a Pith Ball electroscope, Meter stick, Mirror Ruler, Rabbit fur, dark gray nylon rod, clear leucite rod, wool, white acetate rod, black hard rubber rod, blue PVC rod, silk, and plastic.

Procedure The procedure was to rub a single material with a single rod for multiple variations. First Rub the chosen rod against the chosen material to transfer the charges to the rod. Next place the rod on the metal where the pith balls strings connect. Depending on how much charge is transferred to the rod, the farther the pith balls would separate. Finally measure the distance of separation between the two pith balls. We did this for

five trials to assure consistency for the results and for 7 to total different combinations. Data Table 1: Determine the Charges for different combinations Charge (C)

Material

Acetate

Rabbit fur

0.0104

1.114 × 10

Acetate

Wool

0.0016

1.714 ×10

Acetate

Silk

0.0005

5.356 ×10

leucite

Plastic

0.0120

1.286 ×10−7

Rabbit fur

0.0005

5.356 ×10

Nylon

Plastic

0.0036

3.856 ×10−8

PVC

Rabbit fur

0.0000

0

Hard rubber

Avg. dist. rad

(m/±0.00005)

Rod

−7 −8

−9

−9

Data Analysis 1)

{

{√ ( )

r r T × =F 2l mg r r2 k q2 mg 2 l ∧ Tsinθ = F → → × → q= =F= × 2 2 2 2 2l k Tcosθ=mg kq r r r r F= 2 =mg T 1− 1− 1− r 2l 2l 2l

sinθ=

{

√

( )

√

2) The charges are shown in the data table.

3)Sample data: g=

2 G m1 m 2 0.04 −11 −1 −17 =6.673 × 10 × ×10 =8.8238 × 10 N 2 2 r 11

While −8 2

F=

k q2 4 −5 9 (1.228× 10 ) ×10 =1.246 ×10 N =9 ×10 × 2 2 11 r

The above results indicate a great gap between electrostatic force and gravitational.

4)

√

( )

2

×

r C 2l

The mystery fur was rubbed with the PVC rod and came up with a neutral charge. Since PVC is very negative this means that the mystery fur is very positive. Between rabbit and cat fur, the rabbit fur is much more positive meaning that the mystery fur is rabbit fur.

From the data in table 1, it can be concluded that the higher the charge, the greater the average radius distance for the pith balls. Using examples from the table, leucite and plastic combination has a bigger average radius distance than the nylon and plastic combination since it has a bigger positive charge as the plastic is the same for both but the leucite rod has a bigger positive charge than the nylon charge. According to the lab manual, the more positive the charge the farther separate the pith balls would be which falls in line with the data table above. In the opposite direction, if there is a negative net charge the pith balls will stick together. Discussion The design of the experiment was to help show Coulomb’s law in effect. Unfortunately, there are some potential pitfalls that would affect the results from being true such as not letting the charges rubbed onto the rod go away and quickly moving onto the next trial with remaining charges which would affect the results. The experiment can be improved by finding more materials with more differing starting charge as I feel like the range from positive to negative charge was a bit tight. Conclusion The experiment was executed well and further supported Coulomb’s Law as all of our data fell in line with the law, meaning it agrees with the statement, “The magnitude of the electric force that a particle exerts on another is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.” Reference https://science.iit.edu/sites/science/files/elements/phy/pdfs/Coulomb_s_LawRev.pdf...