_- 1B1a Gizmo Lab Co - Gizmo Lab _ Coulomb_s Force (Honors)

Name: Date: 1-29-24 Student Exploration: Coulomb Force (Static) Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: Coulomb’s law, electrostatic force, vector Prior Knowledge Questions (Do these BEFORE using the Gizmo.) . Have you ever taken clothes out of the dryer and found a sock stuck to your underwear? Static cling is an example of electrostatic forces , or the forces that exist between charged objects. 1. How do you think the sock and underwear became charged? While in the dryer, some electrons were transferred from one item to another. 2. Suppose two socks acquire the same charge. Do you think they would stick together? Explain: They will not stick together because they both carry the same charge. Gizmo Warm-up As clothes are tumbled in a dryer, electrons are rubbed off some items, giving them a positive charge, and deposited on other items, giving them a negative charge. These charged items exert electrostatic forces on one another. You can explore these forces with the Coulomb Force (Static) Gizmo. In its initial settings, the Gizmo shows two objects that each have a charge ( q ) of 10.0 × 10 -4 C (coulombs). Turn on the Show force vector checkboxes for objects A and B . The arrows coming from each object are vectors that represent the electrostatic force. The direction and length of each vector show the direction and magnitude (strength) of each force. 1. Are the vectors for objects A and B pointing together or away from each other? The vectors for objects A and B point away from each other. 2. Are objects A and B attracted together or repelled apart? The objects A and B are repelled apart. 3. Compare the lengths of the vectors. What do you notice? I notice that the lengths of both vectors are equal. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Activity A: The effect of charge Get the Gizmo ready: ● Turn on Show grid . Place object A on the x -axis at -5 and object B on the x -axis at +5. ● Check that Show force vector is turned on for each object. Question: How does charge affect the strength of the electrostatic force? 1. Observe: You can change the charge of each object by entering the desired value in the q A and q B boxes. Observe the force vectors for each of the situations listed in the table below. Based on the force vectors, state whether the objects are repelled from one another, attracted to one another, or if there is no force at all. q A q B Attraction, repulsion, or no force? 1.0 × 10 -4 C 1.0 × 10 -4 C Repulsion -1.0 × 10 -4 C 1.0 × 10 -4 C Attraction -1.0 × 10 -4 C -1.0 × 10 -4 C Repulsion 1.0 × 10 -4 C 0.0 × 10 -4 C No force 2. Make a rule: Complete the following sentences with the words “attract,” “repel,” or “zero.” When the charges are the same, the two objects repel one another. When the charges are opposite, the two objects attract one another. When one of the objects has no charge, the resulting force is zero. 3. Predict: How do you think the magnitude of the electrostatic force between two objects will change if the charge of each object was doubled? If the charge of each object was doubled, I predicted that the magnitude of the electrostatic force between the two objects would increase by half. 4. Measure: Turn on Show vector notation for both objects. Set the charge of objects A and B to 1.0 × 10 -4 C. The force on object A is now -0.90 i + 0 j N. That means that the force is -0.90 N in the x direction and 0 N in the y direction. A. What is the magnitude of the force on object A ? | F A | = 0.9 N B. What is the magnitude of the force on object B ? | F B | = 0.9 N C. The force on object A is negative. What does this indicate about the direction of the force? The negative force indicates that the force on object A is directed to the left. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Activity B: The effect of distance Get the Gizmo ready: ● Turn on Show distance . ● Set q A to 10.0 × 10 -4 C and q B to 1.0 × 10 -4 C. Question: How does distance affect the strength of the electrostatic force? 1. Observe: Move object A back and forth. How does the distance between the objects affect the strength of the electrostatic force between them? The distance between the objects causes the magnitude of the electrostatic force to decrease and the objects will move apart. 2. Predict: How do you think the electrostatic force between two objects would change if the distance between the two objects was doubled? It thinks that doubling the distance between two objects weakens the attraction/repulsion, reducing it to 1/4 of its original value. 3. Measure: Place object A on the x- axis at -2, and object B on the x- axis at +1. A. What is the magnitude of the force on object A ? | F A | = 100 N B. What is the magnitude of the force on object A ? | F A | = 100 N C. What is the magnitude of the force on object B ? | F B | = 100 N 4. Gather data: Check that q A is 10.0 × 10 -4 C and q B is 1.0 × 10 -4 C. For each position of object A , record the distance between the objects and the force on object A . Object A Object B Distance (m) | F A | (N) Distance factor Force factor 1 Dist. factor 2 (-2, 0) (1, 0) 3.0 m 100 N 1 1 1 (-5, 0) (1, 0) 6.0 m 25 N 2 0.25 0.25 (-11, 0) (1, 0) 12.0 m 6.25 N 4 0.0625 0.0625 (-14, 0) (1, 0) 15.0 m 4 N 5 0.04 0.04 5. Calculate: To calculate the distance factor, divide each distance by the original distance (3 m). To calculate the force factor, divide each force by the original force (100 N). A. How does the force change as the distance increases? The force reduces as the distance grows. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

B. Now find the reciprocal of each distance factor squared. What do you notice? The force factor equals the reciprocal of the squared distance factor. 6. Apply: What would you expect the force to be if the distance was 30 meters? I would expect the force to be 1 N if the distance was 30 meters. How did you come up with your answer? 10 (30 m ÷ 3 m) 0.1 x 0.1 = 0.01 0.01 × 100, or 1 N Use the Gizmo to check your answer. 7. Make a rule: Based on what you have learned, write an equation to calculate the force between two objects if the product of their charges is 1.0 × 10 -7 C. Use the Gizmo to test your formula. (Note: Use the variable R for the distance between the charges.) F = 900/R² 8. Summarize: Fill in the blanks. The electrostatic force between two objects is proportional to the reciprocal of the distance squared. 9. Challenge: Coulomb’s law is an equation that relates the electrostatic force between two objects to their distance and charge. In activity A, you found that the electrostatic force between two objects is proportional to the product of their charges. Combine that with what you have learned in this activity to complete Coulomb’s law below. (Hint: In the equation, k is a constant.) Check your answer with your teacher. Click the image to select EDIT to use the text box. 10. On your own: Use the Gizmo to find the value of k in the formula above. List the value and describe how you found it below. The units of k are newton · meter 2 ÷ coulombs 2 , or N·m 2 /C 2 . Check your answer with your teacher. k = 8.9 x 10 ⁹ Show your work: q A = 10.0 × 10 ⁻⁴ C q B = 1.0 × 10 ⁻⁴ C R = 30 m F q = 1 N F q = k(q A ·q B /R²) Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved