'45 ASSIGNMENT 3 Part One: Electrostatics 1. Complete each of the following statements by responding with the missing wordis}. t l : a. A positively charged glass rod is brought close to a neutral metal rod. The metal rod is momentarily grounded and then the ground is removed. The positively charged glass rod is removed. and the metal rod is left with a net charge. This method of charging is called charging by I: 1 : b. At the end of the procedure, the sign of the charge on the metal rod is and the glass rod is t l : c. Human hair is rubbed against Styrofoam. This method ct charging is charging by t l : d. At the end of the procedure, the sign of the charge on the hair is and the Styrofoam is t l : e. An ebonite rod with a charge of -E is touched to an uncharged pith ball. This method of charging is .' i : f_ At the end of the procedure the sign and the amount of charge on ebonile rod and pith ball is Answer: [2: 2. A child rubs a balloon on her head. Electrons are transferred from the hair to the balloon. The child then places the balloon in contact with a neutral ceiling. The balloon does not fall but remains in contact with the ceiling. Explain how the charged balloon is electrostatically attracted to the neutral ceiling. f2: 3. a} Use your knowledge of insulators and conductors to suggest a material that could be used for a} the wire component and b} the insulating cover of an extension cord. b) Explain why you should not use an indoor extension cord in your backyard. Use the concept of insulation to explain, and conduct (pun intended) research to find support for your answer. Include the URL of the website(s) where you found your information. (2) 4. Summarize how a lightning strike occurs by completing the following statements: (0.5) a. When water molecules in a churning cloud formation collide with each other the result is (0.5) b. The top of the cloud becomes positive and the bottom negative because (0.5) C. A conducting plasma is formed due to (0.5) d. The separation of charge at Earth's surface is cause by (0.5) e. A streamer is formed when air molecules near Earth's surface(0.5) f. A lightning strike occurs when 5. The diagram below shows the apparatus used in an electrostatics experiment. negatively charged rod grounding rod uncharged electroscope a. Describe or draw what is observed when a negatively charged rod is placed beside the top of the electroscope and why the observed effect occurs. (2)Physics 30: Assignment 3 5 (2) b. While the rod is held close to the top plate of the electroscope as in part a, the grounding rod makes contact with the plate. Describe what happens to the leaves and why. (2) c. Next, the ground is removed and the rod is withdrawn. A net charge is left on the electroscope. Identify the sign of the charge and explain why this charge is left on the electroscope. You may answer with any combination of words and diagrams. (3) 6. Describe an experimental procedure that you could use to determine the unknown charge on a metal sphere without changing the charge on the sphere. The diagram below shows equipment available for you to use. ebonite rod fur charged uncharged sphere electroscopePhysics 3D: Assignment 3 . ' : T. Drain.r a diagram of a pith ball that is neutral and a pith ball that is negatively charged. E: 8. Objects obtain charge via friction, conduction or induction. In each situation, the existing charges transfer, no newI charges are created. a} Identify the type of subatomic particle that moves between objects. bi Identify the number of the corresponding physics principle from your data sheet. Physics 30: Assignment 3 Part Two: Investigating Coulomb's Law 1. While investigating Coulomb's Law, physics students devised an experiment to better understand the relationship between the force of electrostatic repulsion acting on two charged objects and the distance of their separation. Results of the experiment are shown in the table below. Separation Distance Magnitude of Force of Repulsion (r) |F| (N) ( x 10-2 m or cm) 1.00 360.0 2.00 89.9 3.00 40.0 4.00 27.5 5.00 14.4 (3) a. Draw & insert a graph of the results shown in the table.(1) b. What does the shape of the graph indicate regarding the relationship between the electrostatic force and the separation distance between the two charges? (2) c. Complete the third column in the table below with an expression using r which can be used with F to plot a linear graph (i.e., straighten the graph). See workbook page 5 for strategies on curve straightening. Separation Magnitude of Distance Force of Repulsion (r) |F| (N) ( x 10-2 m or cm) 360.0 1.00 89.9 2.00 40.0 3.00 27.5 4.00 14.4 5.00to! d. Draw 3; insert a graph oi the data in the revised table above. A student is investigating Coulomb's law. The student measures a force of +2.Dx1'3 N between the two charged spheres. .2 1 : a. Describe the law that Charles Coulomb used as the basis of his hypothesis. .22: b. Describe t1.Ivo methods the student could use to increase the force to 54 times its current value. Your answer should include numerical values for clarity. (2) c. The student touches one of the spheres with a neutral sphere of equal size and then removes the neutral sphere. The student then moves one of the spheres so the distance is four times the original distance. What is the ratio of the original force to the new force? (1) 3. Briefly describe Coulomb's torsion balance experiment. (2) 4. What two relationships are investigated in Coulomb's torsion balance experiment