Tanner Rich, Stanley Archer, Donald French

University Physics 2 sec1

Thursday @ 2pm

9-3-15

Electrostatic Phenomena

Intro:

This lab’s purpose was to get us familiar with electricity and how it works. Electricity is basically

the flow of different charged electrons to an oppositely charged item. These electrons can become

charged by rubbing to materials together. The material that loses electrons is positively charged and

vice versa. The items needed in this lab were: 2 rubber rods, wool fur, electroscope, sulfer, wooden

ruler, metal pole, glass rod, electrophorus, silk and cork dust. In our experiment, our rubber rod was

negatively charged and the fur we rubbed it with was positively charged.

Procedure:

1. We were to rub the fur on the rubber rod so that the rod would be negatively charged.

Then once we had a charge in the rod, we were to put the rod near some cork dust and

observe what happened.

2. We were to get 2 charged rubber rods and hang one of them up by a piece of string and

then point the charged tip to the other tip. Next we were to charge the suspending rod

again and put the fur close to it and record what happened.

3. We obtained an uncharged electroscope and placed the charged rubber rod near the

electroscope’s knob. After we did that, we were to touch the knob with a finger and

observe/explain what happened.

4. We were to charge the electroscope negatively by using the rubber rod and place the

various items ( sulfur, uncharged rod, dry wood, metal, and glass rod) and record/explain

what happened. Then after seeing what happened, put them in order of increasing

conductivity.

5. We were to charge the electroscope by induction and make pictures to show how this

works.

6. We were to charge the electroscope by induction, which makes it positively charged, and

then place the charged glass rod on the knob. After seeing what happened, we were to

explain what kind of charge was on the glass rod.

7. We were to charge the electroscope with the rod making it negatively charged. Then we

were to rub the electrophorus with the wool and touch it so that it would be charged by

induction. The we would place the disk near the knob of the electroscope and record what

happens. Then repeat with a positively charged electropscope.

8. We were to charge the plate again and touch it to one of our ears and record what happens.

*note that the numbered list above corresponds the numbered list below

Analysis:

1. After rubbing the rubber rod with the fur, the rod became negatively charged, which then

caused the positively charged cork particles to attract to the rod. The cork particles

attached themselves to the rod and after a certain amount of cork particles attached

themselves, the particles would jump off since that there was more of a positive charge

form the other particles then there was of a negative charge from the rod.

2. When the 2 negatively charged rods were put close to each other, they repelled. Then we

put the fur near the rod, and as a result the fur was attracted to the rod. So in conclusion,

like charges repel each other and opposite charged attract.

3. When the electroscope became charged, the metal piece and the leaf separated. Then

when we touched the knob on the electroscope, the metal piece and the leaf went back to

their normal position (touching). Then we recharged it with the rod and touched the fur to

it. The fur made it shoot back to its normal position. Figure 1 shows a visual demonstration.

Figure 1

4. From least conductive to most conductive (determined by how fast the leaf went back to

normal position): sulfur, rubber, wood, glass rod, and metal.

5. Figure 2 shows how we successfully charged our electroscope by induction.

Figure 2

6. The glass rod is negatively charged when rubbed with silk. We know this because the

rubber rod negatively charged the electroscope and when we placed the glass rod on the

knob, nothing happed (the leaf remained outward). This further proves that alike charges

repel.

7. We found out that the metal disk is positively charged. When the leaf was charged with a

negative charge, we touched it with the metal and the leaf went back to normal position. So

the positively charged metal balanced out the negatively charged leaf. Then when the leaf

was it normal/ neutral position, we then placed the metal of the knob and the knob became

erect/ positively charged again. Which proves that the metal disk (electrophorus plate) had

a positive charge.

8. When we placed the positively charged plate to our ears. We all felt a slight shock. This was

from the transfer of electrons coming to our skin. Better known as the classis static shock

that many of us used to prank each other as kids.

Conclusion:

Overall we would consider this lab a success. We achieved all of our desired results and was

able to prove scientific law with electricity. However, there were some difficulties in this lab. 0ne of

these was that it was very hard to get a charge on the rubber rod. Since that the fur and the rod were

so old, they just didn’t want to give us a charge. We had to rub the rod violently with the fur to get a

charge. We also discovered that we had to try a numerous amounts of combinations of fur in rod to get

a charge. Also, when it was charged, we had to act fast because the water vapor balanced out the

charge fairly quick.