Copy of 10252769.1c Balloon Charge Lab V1 _ How many electrons moved_ HONORS _

1B | Balloon Charge Lab: How many electrons moved? Problem: Bill Nye the Science Guy did an experiment with static electricity. [ Video link ]. We are curious to find out how many electrons were transferred from his hair to the balloons to make the balloons repel each other. Task #1 : Prepare the model. 1) Blow up two balloons to approximately equal size. Mass of Blown-Up Balloon - Before Charging Mass of Balloon 1 = g = kg 3. 6 0. 0036 Mass of Balloon 2 = g = kg 4. 7 0. 0047 Average Balloon Mass = g = kg 4. 2 0. 0042 2) Using a 1.0 m string, tie balloons together. 3) Using a consistent process and/or time for each balloon, charge each balloon using your hair. (e.g. Rub each balloon up and down for 5s). 4) Without touching the newly charged balloons on anything or anyone, drape the balloon string over the end of a meter stick, allowing for equal lengths on each side. One person will need to hold the meter stick out away from themselves to try to keep the balloons from being drawn toward them. 1

Task #2: Document model setup and dimensions. Balloon 1 Balloon 2 Diagonal distance from top of meter stick to center of Balloon 1 = m 0. 69 Diagonal distance from top of meter stick to center of Balloon 2 = m 0. 67 Vertical distance from top of meter stick to center of Balloon 1 = m 0. 75 Vertical distance from top of meter stick to center of Balloon 2 = m 0. 75 Horizontal distance center-to-center between Balloons 1 and 2 = m 0. 35 Add horizontal, vertical measurements to the diagram below: You will use this geometry to help determine the angle of your string . Show ALL calculations for determining the angle. [Click on drawing and select Edit in the lower left corner] 2

T = N 0. 045 arctan(.35/.75) = 25 degrees cos(25) = Ty/T 0.041/cos(25) = t 6 T = 0.045 F e = N 0. 0204 Task #4: Extend the model. Using Coulomb’s Law and the electric force, F e , found for your model, determine the charge, q 1 and q 2 , for each balloon. Show ALL calculations. F e = k C (q 1 q 2 )/ r 2 k C = 8.99 x 10 9 Nm 2 /C 2 q 1 × q 2 = (F e × r 2 )/k c q 1 × q 2 = 0.0204(0.35) 2 /8.99 x 10 9 q 1 × q 2 = 0.002499/8.99 x 10 9 q 1 × q 2 = 2.781 x 10 -13 q 1 = q 2 = √(2.781 x 10 -13 ) q 1 = q 2 = 5.273 x 10 -7 Average Charge, q = C 2. 781 𝑥 10 −13 Charge of Balloon 1, q 1 = C 5. 273 𝑥 10 −7 Charge of Balloon 2, q 2 = C 5. 273 𝑥 10 −7 (continue on next page) 4

Task #5: Draw conclusions from the model. a. What is the average number of excess electrons that were transferred to either balloon? Number of excess electrons = q 1 /(1.602 x 10 -19 ) Number of excess electrons ≈ (5.273 x 10 -7 ) / (1.602 x 10 -19 ) Number of excess electrons ≈ 3.29 x 10 12 b. The mass of an electron is accepted to be 9.109 x 10 -31 kg. How much mass was transferred to the balloon when the electrons moved? Mass transferred = Number of excess electrons × mass of one electron Mass transferred = (3.29 x 10 12 )(9.109 x 10 -31 ) Mass transferred ≈ 2.995 x 10 -18 kg c. The radius of an electron is accepted to be 2.82x10 -15 m. If all of the excess electrons transferred to one of your balloons were lined up end to end, how far would they stretch? Total length = Number of excess electrons × radius of one electron Total length = (3.29 x 10 12 )(2.82 x 10 -15 ) Total length ≈ 9.28 x 10 -3 m 5