lab report

Student’s name
Professor’s name
Course
DateElectrostatics Lab

Objectives
To verify the existence of the two types of electrostatic charges (positive and negative) and understand them.
To understand, as defined by the Coulomb’s law, how the electroscope behaves when charged rods are close to it interacting with the present charges in the electroscope.
To visualize the transfer of charges between the electroscope, charged rods and other objects and to comprehend how the charges are recorded by the electroscope.
Introduction
Electrostatic is a term used to define stationary charges. All materials are comprised of two charges; positive and negative charges. In metals (conductors) negative electric charges move freely while in plastics (insulators), electric charges are fixed.
Electroscopes are devices that are used to identify the absence or the presence of electric charges. They are in different forms but essentially, they have metallic rings that support a metal post with an aluminum needle rotating inside the ring. An insulating plastic separates the ring from the post to prevent a charge flow from the post to the ring. The charge, however, can flow from the metal post to the needle.
Coulomb’s laws state that charges exert forces on each other when brought closer to one another. Like charges repel each other while unlike charges attract each other (Davies 393).
Materials
1 each electroscope kit with electrostatics accessories
1 grounding wire with an alligator clip
Procedure
Exercise 1: Inducing a Charge on the Electroscope
A circular disk terminal was positioned on the electroscope then a ground wire was used to touch the top metallic terminal of the electroscope to ground it.

Once the needle was in the correct position (pointing straight up), the ground wire was taken off. The PVC rod was then charged negatively by rubbing it with the wool. The charged rod was then moved closer to the circular disk on top of the electroscope while avoiding the rod from touching the disk. Observations were made. The process was then repeated using the acrylic rod (positively charged).
Exercise 2: Charging the Electroscope by Conduction
The electroscope was earthed then the charged PVC rod was used to touch the disk and then the rod was moved away. Observations were made. Without earthing the electroscope, the charged PVC rod was then moved closer to the disk but not touching it. Observations were also made during the exercise.
To double check the understanding, an acrylic rod rubbed with silk was brought closer to the electroscope touched at the beginning with the charged PVC rod and then observations were made.
The above process was then repeated but the charged acrylic rod was used to touch the electroscope that was initially uncharged.
Exercise 3: Charging the Electroscope Induction
The electroscope was earthed then, the charged PVC rod was brought close to one side of the disk but not touching it while, simultaneously, the edge of the electroscope disk was being touched with a grounded wire. The grounded wire was then removed before moving the PVC rod away. Observations were made. The above process was then repeated using a charged acrylic rod.
Observations and Explanations
Exercise 1: Inducing a Charge on the Electroscope
When a charged rod was moved closer to the disk, the aluminum needle deflected. A charged rod caused the charges to move accordingly. When a negatively charged PVC rod was brought closer, it repelled the electrons on the disk causing the needle and the post to be both negatively charged hence the deflection since the like charges repel each other.
left1657340084772517589500The PVC rod is negative, the top and the bottom is negative
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The needle deflected
When the positively charged acrylic rod was brought closer, it attracted electrons to the disk leaving the needle and the post to be positively charged. Thus, the deflection of the needle.
02286000068516527178000The acrylic is positive, the top is negative, the bottom is positive. The needle deflected
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When the rods were moved away the needle moved back towards its vertical position since the electrons were moving to neutralize the charges that were induced by the charged rods.
Exercise 2: Charging the Electroscope by Conduction
When the charged PVC rod was touched, the disk it transferred the negative charge to the electroscope and when it was moved away the needle remained deflected. When the PVC was brought closer without touching the disk, the needle deflected more. When the acrylic rod was brought closer, the needle repelled less.
When the acrylic rod was used to touch the electroscope, it took away the electrodes thus, charging the electroscope positively. The needle remained deflected when the rod was moved away but deflected more when it was brought closer. When the PVC rod was brought closer, the needle deflected less.
Like charges repel and that is why the needle deflected more when the rod with similar charge as the electrode was brought closer. On the other hand, unlike charges attract each other hence when a charge of opposite charge to the electrode was brought closer, the needle deflected less.
Exercise 3: Charging the Electroscope by Induction
When the negatively charged PVC was brought near the disk, it induced a charge on the electroscope. When the disk was touched electrons were transferred from the ground to the disk to neutralize the positive charge, the needle and the post remained negatively charged and it was deflected even after the rod has been moved away. When the PVC was brought closer without touching the disk, the needle deflected more. When the charged acrylic rod was moved closer, the needle repelled less.
Similarly, when the charged acrylic rod was brought near the disk, it induced a charge in the electroscope. When the disk was touched electrons were transferred to the ground from the disk the needle and the post remained positively charged and it was deflected even after the rod has been moved away but deflected more when it was brought closer. When the negative PVC rod was brought closer, the needle deflected less.
Like in exercise 2, like charges repel and that is why the needle deflected more when the rod with similar charge as the electrode was brought closer. On the other hand, unlike charges attract each other hence when a charge of opposite charge to the electrode was brought closer, the needle deflected less.
Conclusion
All materials are comprised of two charges; positive and negative charges. A material can be charged by either transferring electrons (negative charge) from it or to it. Charges exert forces on each other when brought closer to one another as stated by the Coulomb’s law. We achieved the objectives of the lab.

Works cited
Davies, G. R. “An electronic gold leaf electroscope.” Physics Education 9.6 (1974): 393.