Static Electricity Lab Report PDF

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Physics 2 Static Electricity Lab Report...

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STATIC ELECTRICITY BACKGROUND The word electricity comes from the Greek word electron which means amber (a tree resin that has been fossilized). When rubbed, a piece of amber can attract small objects like tiny pieces of paper. Later, other materials were found which exhibited this same behavior. Today we know that the source of this attraction is due to the presence of static electric charge. Electric charge comes in two forms: positive and negative. Electrons carry negative charge and protons carry positive charge. Most materials are electrically neutral – they have an equal number of positive and negative charges (thus an equal number of protons and electrons). Static electricity occurs whenever you have an accumulation of one type of charge. This can happen when two non-conducting materials are rubbed together – for example plastic and fur. A static charge is produced because some electrons are transferred from one object to the other. The material losing electrons now has fewer electrons than normal and becomes positive. The material gaining electrons now has more electrons and becomes negative. Surrounding a charge there is an invisible electric field which gets weaker the farther away one gets from the charge. Electric field lines are typically drawn to visualize the field. For a positive charge, the field is directed outward from the charge (figure 1a). For a negative charge, the field is directed inward towards the charge (figure 1b). As a result, like charges repel each other and unlike charges attract each other.

a b Figure 1. illustrates the direction of the field in a positive and negative charge. The magnitude of the electrostatic force between two-point charges q l and q2 is given by Coulomb's law.

where r is the distance between the two charges and k is called the proportionality constant and is equal to 9 x 109 N.m2/C2. The direction of this force is determined by the sign of the charges: like charges repel and unlike charges attract and acts along the line between the two point charges. If a neutral material is placed inside a weak electric field, it will not experience a net force, because it contains an equal number of positive and negative charges. However, if a neutral object is placed inside a strong electric field, the material may become polarized. Inside a polarized material, positive and negative charges are no longer randomly distributed and are slightly separated (positive on one side, negative on the other).

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Figure 2. Distribution of charges in a polarized and non-polarized object Using Coulomb’s law, we can explore the effect of the distance, between two charged particles, on the force between them. This force decreases as the distance between the charges increases. The electric field surrounding a charged object gets weaker with distance, the object will have a stronger attractive force on its closest charges of opposite sign and a weaker repulsive force on the like charges farther away. Thus, the polarized material will experience a net attractive force. For example, if you charge a balloon by rubbing it on your hair, it can stick to a neutral wall. In a metal, a charge can move freely and stay on the surface. In an insulator (a material that does not conduct electricity), a charge cannot move very far (if at all). Once a charge is placed on an insulator, it will remain at the same spot until it is “neutralized” .

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STATIC ELECTRICITY LAB REPORT Name(s): ------------GOAL: (briefly state what experiment(s) will be performed and with what purpose) The purpose of this lab was to understand the idea of electrostatics AKA static electricity, and how electric charges interact with one another. The lab helped explore concepts of static electricity and discover how many types of electrical charges exist and how they interact with each other. After completing these experiments, it was observed that like charges repel one another and opposite charges attract. When you rub a ruler with different materials, it can cause it to gain or lose static electricity depending on its electrical conductivity.

Part 1 Purpose This laboratory activity provides the opportunity to investigate the concepts of static electricity, electrical force, charge, and polarization. Open the following links: Coulomb’s Law: https://phet.colorado.edu/sims/html/coulombs-law/latest/coulombs-law_en.html Charge laboratory: https://phet.colorado.edu/sims/html/balloons-and-static-electricity/latest/balloons-and-staticelectricity_en.html The lab will have two parts describing what is happening at both macro and atomic scales. 1. Rub a balloon on your sweater and stick it to the sweater. 2. Write down what you think is happening. Have a few students share their thinking as part of the class discussion. Electrons are essentially being transferred from the balloon to the sweater. Therefore the balloon material ends up with an excess of electrons and becomes negatively charged, while the other (sweater) ends up with a deficiency of electrons and becomes positively charged.

3. Display the Balloons and Static Electricity sim with the charges hidden. Rub the balloon on the sweater and have it stick on the sweater like you did with the real objects. Then turn on the Summer 2020

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SHOW ALL CHARGES and ask the students to “write observations and include drawings” and then repeat the demo using the sim. Hit RESET to do this several times. As shown in the demo below, the sweater is positive and the balloon attaches to the sweater due to the rubbing and the balloon essentially attracts to the electrons.

4.Ask “Reflect on your answer to #2, write down how your thinking has changed.” Have a class discussion. Include in the discussion the vocabulary: charge transfer and electric attraction. Electrons are being transferred from the balloon to the sweater. Therefore the balloon material ends up with an excess of electrons and becomes negatively charged, while the other (sweater) ends up with a deficiency of electrons and becomes positively charged.

5. Show how a real balloon can stick on the wall. “Write what you think is happening.” Follow with sharing and discussing. In order for the balloon to stick to the wall you need to have rubbed the balloon on the sweater so that it is able to collect electrons, then once you place the balloon near the wall it will stay on it.

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6. Repeat the demo using the sim with the charges on. “Write observations with drawings of what happens” and then repeat the demo. Hit RESET to do this several times. Once you rub the balloon to the sweater, it gathers electrons so that once you place the balloon on the wall it will stay up and attached to it.

7. “Reflect on your answer to #5, write down how your thinking has changed.” Have a class discussion. Include in the discussion the vocabulary: induction; compare with charge transfer and electric attraction. Wool is a conductive material, which means it readily gives away its electrons. Consequently, when you rub a balloon on wool, this causes the electrons to move from the wool to the balloon's surface. When the balloon has been rubbed enough times to gain a sufficient negative charge, it will be attracted to the wall.

8. “Reflect on your answer to #6, write down any new ideas that you have.” Have a class discussion. Include in the discussion the vocabulary: electric repulsion; compare with charge transfer, induction and electric attraction. Wool is a conductive material, which means it readily gives away its electrons. Consequently, when you rub a balloon on wool, this causes the electrons to move from the wool to the balloon's

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surface. When the balloon has been rubbed enough times to gain a sufficient negative charge, it will be attracted to the wall. Although the wall should normally have a neutral charge, the charges within it can rearrange so that a positively charged area attracts the negatively charged balloon. Because the wall is also an electrical insulator, the charge is not immediately discharged.

9. Show how an electroscope is used to measure charge by rubbing the balloon and bringing it near the scope. My scope will show a difference between rubbing more than less. One common demonstration performed with the electroscope involves the induction process of charging. In the induction process of charging, a charged object is brought near to but not touching the electroscope. The presence of the charged object above the plate of the electroscope, induces electrons within the electroscope to move accordingly. With the charged object still held above the plate, the electroscope is touched. At this point electrons will flow between the electroscope and the ground, giving the electroscope an overall charge. When the charged object is pulled away, the needle of the electroscope deflects, thus indicating an overall charge on the electroscope.

10. Draw an electroscope and a balloon like the picture on the right. Say “Draw this on your paper and sketch what you think is happening to make the electroscope parts move apart.” Then have a student draw his model on the board and follow with a class discussion. One common demonstration performed with the electroscope involves the induction process of charging. In the induction process of charging, a charged object is brought near to but not touching the electroscope. The presence of the charged object above the plate of the electroscope, induces electrons within the electroscope to move accordingly. With the charged object still held above the plate, the electroscope is touched. At this point electrons will flow between the electroscope and the ground, giving the electroscope an overall charge. When the charged object is pulled away, the needle of the electroscope deflects, thus indicating an overall charge on the electroscope.

11. Touch the electroscope to ground it. Demonstrate several times and say “Draw what you think is happening.” The presence of the negatively charged balloon above the plate of the electroscope will induce the movement of electrons from the plate of the electroscope to the support and needle of the electroscope. This is explained by the like charges repel principle. The negatively charged

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balloon repels the negatively charged electrons, thus forcing them to move downwards. Once the electrons leave the plate and enter the needle, both plate and support/needle acquire an imbalance of charge. The plate acquires an excess of positive charge (since electrons have left this once neutral region) and the support/needle acquires an excess of negative charge (since electrons have entered this once neutral region).

12. Bring up John Travoltage. (https://phet.colorado.edu/en/simulation/john-travoltage) Rub John’s foot on the floor to demonstrate charge transfer. Talk about the similarities and differences in the two models represented by the sims. Touch his finger to the door knob to show grounding. Make sure that they understand that this is commonly called grounding. Say “Discuss with your partner what is happening when he touches the knob.” Repeat the demo several times. In the demo John Travoltage is basically attaining negative electrons/particles due to stepping and rubbing his foot on the carpet, once he touches the door knob that is metal he is shocked or slightly electrocuted.

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Part 2 This part uses the Charges and Fields simulation from PhET Interactive Simulations Learning Goals: Students will be able to describe and draw models for common static electricity concepts. (transfer of charge, induction, attraction, repulsion, and grounding) 1. Open https://phet.colorado.edu/sims/html/balloons-and-static-electricity/latest/balloons-andstatic-electricity_en.html, Explore to develop your own ideas about electrical charge. Then, describe some of your experiments and your observation with captured images from the simulation.

2. Open John Travoltage at https://phet.colorado.edu/en/simulation/john-travoltage then explore to develop your own ideas about electrical charge.

Test your understanding: Without using the simulations, predict the answers to these questions, then use the simulation to check your ideas.

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Question 1: When the balloon is rubbed on the sweater, what might happen? A neutral balloon will gain electrons from the sweater. Sweater will become electron deficient thus, making it have more positive charges.

What do you predict for the answer? B. Negative charge on the sweater will move on to the balloon. Describe an experiment and include images from the simulation that supports your answer.

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Electrons moved from sweater to balloon like predicted. Question 2: What do you think will happen when the balloon is moved closer to the wall? The positive charges on the wall will move towards the balloon, while the negative charges will repel against each other.

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What do you predict for the answer? A. Some positive charges in the wall will move towards the balloon Describe an experiment and include images from the simulation that supports your answer. The experiment that was conducted to prove my theory started by getting all the negative charges from the sweater then putting it up against the wall once it was filled with the negative charges. The image shows that the negative charges do repel each other and the positive charges remained. Opposite charges attract each other.

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Question 3: What do you think the balloons will do? I think that the balloons will repel each other because they are both negative and do not attract each other.

What do you predict for the answer? B. The balloons will move away from each other.

Describe an experiment and include images from the simulation that supports your answer. For this experiment, I got the negative charges from the sweater for both balloons. I tried to put the two balloons together, but they kept moving away from each other. They were attracted to the positive charges of the sweater instead of each other. So the balloons did move away from each other.

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Question 4: What might happen to the charge on the man when he touches the doorknob? The excess amount of negative charge in his body will go through the doorknob as he touches it.

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What do you predict for the answer? A. Most electrons will go into the knob and down to the earth.

Describe an experiment and include images from the simulation that supports your answer. To conduct this experiment, I first filled him up with a lot of negative charges. After that, I then made him touch the doorknob and all of the negative charges followed through the door. The negative charges quickly left his body as he touched the doorknob as shown below.

Part 3 Review your understanding: Summer 2020

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1. Two balloons were rubbed on a sweater like in the Balloons and Static Electricity and then hung like in the picture below. Explain why you think they move apart and what might affect how far apart they will be. The reason why they do move apart is because wool is a conductor that gives its electrons away which transfer to the balloon. The surface of the balloon now has a negative charge because the object is made up of rubber which is an insulator. the thing that affects how far apart the balloons will be apart is the force q/r^2 determining how far they will repel to come to an equilibrium.

Explain your understanding: 2. Watch the short video demonstration of: https://phet.colorado.edu/en/simulation/electrichockey a. Why can you make a goal without hitting the puck? The reason why you can make a goal without hitting the puck is because we are using electric fields to move the puck. b. Why can you use either a positive charge or a negative charge to move the positively charged puck? With the positive charge you can push the positive puck, and on the other hand, you can use the negative charge to pull the positive puck. c. What do you think would happen if you use 2 charges instead of one to make the puck move? If you use two of the same charges to move the puck, it would move twice as fast, if you use two different charges in the same exact place, nothing would happen because they cancel out. if you use two of the same ones exactly opposite to each other, they would also cancel out and the puck would be stationary. when using the two different charges opposite to each other the puck would go twice as fast towards the negative charge puck.

3. Examine the image with a positive and a negative charge on the playing field with the positive puck. a. What do you think the arrows on the puck are illustrating? The arrows on the puck are illustrating how both the positive and

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negative charges affect the puck when displayed in the hockey game. b. How does the arrow from the positive charge compare and contrast to the one from the negative charge? Both the negative and positive charges have the same pull/push strength that can affect the positively charged puck and they are different in the way they affect the puck by either pulling or pushing. c. Which way do you think the puck will move? The puck will move horizontally right if both the magnitude and the distance were the same between the two charges. d. How would the arrows look if the puck was negative? The arrows would be opposite to what the picture displays. the positive charge would pull and the negative charge would push. 4. Open Charges and Fields. In this simulation, a little different model is used. The little yellow “E field sensors” are like the hockey puck but they are on a high friction surface, so they stay in place allowing for measurements. Collect data by turning on Values & drag in the Tape Measure like in this image:

a. Investigate to check your answers from #2 and #3. Write how the results of your investigation support or change your ideas. The answers from #2 and #3 support the results from the investigation since the same rule applies that similar charges will repel each other and opposite charges will attract each other. b.

Determine the relationship between distance and the strength of the electric field around a charged body. Use a Google Spreadsheet to document your data, graph and determine the equation for the relationship. Insert your data table and graph from your spreadsheet.

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c. Determine the relationship between amount of charge and the strength of the electric field around a charged body. Use Google Spreadsheet to document your data, graph, and determine the equation for the relationship. You can stack charges on top of one another to make the amount of charge vary. Insert your data table and graph from your spreadsheet. Number of Protons

Distance (m)

Voltage (V)

Volts/Meter (V/m)

1

1.51 m

6.07 V

4.03 V/m

2

1.51 m

12.08 V

8.00 V/m

3

1.51 m

18.10 V

12.0 V/m