PHYS 1415 Lab 06: Electric Charges Objectives: 0 To discover some of the interactions of particles that carry electric charges. 0 To determine the likelihood of getting a \"carpet shock\" (based on controllable variables), and to avoid or produce such shocks under a series of challenging conditions Exploring the Nature of Electrical Interactions You can investigate the properties of electrical interactions between objects using the following material: - roll of Scotch Magic tape Try the activities suggested below. Mess around and see if you can design careful, logical procedures to demonstrate that there must be at least two types of charge. Carefully explain your observations and state reasons for any conclusions you draw. Activity 1 1. You should tape a 10 cm or so, 2 strips of Scotch Magic tape, onto a wooden table. The end of each tape should be curled under to make a non-stick handle. Peel your tapes off the table and bring the non-sticky side of the tapes toward the other non-sticky side. Hold both strips vertically. Question 1: Describe your observations. Do the strips attract, repel or not interact? 2. Tape two more strips of tape with "handles" on the table and use a pen to label them \"B" for bottom. Press a second strip of tape on top of each of the B pieces and give it a handle. Label these strips \"T\" for top. [cpl l ) mm -. - l , |1\\[\"i]'\\2 Z _'r=,'' lmirurn ill: drip. \\ itilllitldlli'll s'ri)' 3. Pull each pair of strips off the table. 15" '_ l4 1 4. Then pull each top and bottom strip apart quickly. (Note: you will need to repeat this set of procedures several times to answer all the questions below.) Question 2: Describe the interaction between two top (T) strips when they are brought near each other. Do the strips attract, repel or not interact at all? Question 3: Describe the interaction between two bottom (B) strips when they are brought near each other. Do the strips attract, repel or not interact at all? Question 4: Describe the interaction between a top (T) and a bottom (B) strip when they are brought near each other. Do the strips attract, repel or not interact at all? Question 5: Are your observations of the tape strip interactions suggest that there are two types of charge? Explain your answer carefully, in complete sentences, and using the results of all your observations. Question 6: Do like charges repel or attract each other? Do unlike charges repel or attract each other? Explain based on your observations. Question 7: Based on your observations of the movement of the tapes, how does the strength of these forces compare to the gravitational force on the tapes near the surface of the earth? Activity 2: PHET Simulations Discussion When you walk across a carpet and touch a metal doorknob, you might feel a small shock. The friction between the different materials in your footwear and the carpet gives you a static charge. (Physicists call it a triboelectric charge, meaning a charge from frictional contact.) The metal doorknob is a conductor, so the excess charge on your body jumps to the knob rapidly, creating the spark. Your nerves are sensitive to electrical impulses, so you feel the shock. In the simulation, John Travoltage's foot can be rubbed across a carpet so that his body collects charge. His arm can be rotated so that a spark will jump from his finger to the doorknob. 1. Open the PhET simulation John Travoltage (https://phet.colorado.edu/en/simulation/john- travoltage). 2. Rub John Travoltage's foot back and forth against the carpet until a sparkjumps from his finger to the doorknob. Question 8: Explain what happens when John rubs his foot on the carpet. Question 9: What do the blue spheres represent? Question 10: How does John Travoltage react when the sparkjumps? 3. Move John Travoltage's hand close to the doorknob, then rub his foot on the carpet again. Question 11: Compared to the process you observed in Step 2, what happens differently this time? Question 12: How can you get the maximum charge built up on John Travoltage without producing a spark? Question 13: Under what circumstancesif anywill a spark jump from John Travoltage's foot to the doorknob? Why do you suppose this is (in terms of the physics involved)? 4. Rotate John Travoltage's arm so that his finger is pointing directly at the doorknob. Carefully rub his foot against the carpet without producing a spark. Question 14: What is the greatest number of charges you can get onto John Travoltage's body? (How many small spherical charges can be collected on his body before a discharge occurs?) Summing up: Under which conditions is a spark most likely to jump between John Travoltage and the doorknob? Describe in terms of the amount of charge on his body and the distance between his hand and the doorknob. 5. Open the PHET simulation Balloons and Static Electricity (https://phet.colorado.edu/en/simulation/balloonsandstaticelectricity) Question 15: What happens to the electrons (minus signs) on the wool sweater as you put the balloon near it? Question 16: What do you have to do to remove all electrons from the sweater? How can we transfer charges? Question 17: What happens when you release the balloon? Question 18: Click on \"Reset Balloon\". What happens when the balloon is moved closer to the wall? Now bring the balloon close to sweater. Once the balloon acquires negative charges, would the balloon be attracted to a neutral surface like the wall? Question 19: How can you make two balloons stick to the sweater? Question 20: How can you make two balloons move apart from each other? Question 21: Does an object have to have an electrical charge to be attracted to an electrical charge? Give an example. Summing up: Summarize the important charge properties