Good Luck! Mlanie LaRoche-Boisvert - Electromagnetism Electromagnetism and Optics - Winter PH. Electromagnetism and Optics - Winter PH

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1 1 2 Notes: 1. To submit a problem, just click the Submit button under it. The Submit All button is not necessary. 2. A problem accepted as correct by CAPA will be highlighted in green. Once you see this, your problem has been submitted and accepted as correct.<br/ > 3. If you are trying to obtain the correct number of significant digits, use the E notation. I.e = 100. is wrong, but = 1.0e2 is right in the number of significant digits. 4. Use period. to denote decimal point. comma, doesn t work here. <br/ > 5. You are encouraged to solve all the problems independently. For questions about the assignment itself, please consult one of your tutors. If you have any questions about the capa system, don t hesitate to contact capa142@physics.mcgill.ca, i ll be glad to help you. Good Luck! Problem 1 Consider two separate systems, each with four charges of magnitude q arranged in a square of length L as shown above. Points a and c are in the center of their squares while points b and d are half way between the lower two charges. Determine whether the following statements are True or False. A. B. C. D. Choices: True, False. The electric field at a is zero. The electric potential at c is zero. The electric potential at a is zero. The electric field at c is zero. You are correct. Your receipt is Problem 2

2 3 a) The figure below shows two points in an E-field: Point 1 is at (x1,y1) = (4,4) in m, and Point 2 is at (x2,y2) = (13,9) in m. The Electric Field is constant, with a magnitude of 59.0 V/m, and is directed parallel to the +x-axis. The potential at point 1 is 1000 V. Calculate the potential at point 2. 4 Consider a vertical line of length L=0.900 m and uniform positive charge per unit length λ=2.2 µc. Point A is a horizontal distance x=0.25 m from the center of the line, while B is the same horizontal distance from the line but is at a vertical distance y=0.26 m from point A; point C is a further vertical distance z=0.050 m above point B. (see figure) Y. C B 2. 1 y X y+z A You are correct. Your receipt is b) Calculate the work required to move a negative charge of Q = -516 µc from point 1 to point 2. x You are correct. Your receipt is Problem 3 Answer true or false for the following statements. Choices: True, False. A. a) The potential at A is higher than the potential at B. B. b) The potential at B is higher than the potential at C. C. D. E. F. c) The electric field has a horizontal component at A. d) The electric field has a horizontal component at B. e) The electric field has a vertical component at A. f) The electric field has a vertical component at B.

3 5 Problem 4 Two point charges each of magnitude 2.03 µc are located on the x axis. One is at x= 1.17 m, and the other is at x = -1.17m. a) Determine the electric potential on the y axis at y = 0.541m. You are correct. Your receipt is b) Calculate the electric potential energy of a third charge, of µc, placed on the y axis at y = m. You are correct. Your receipt is Problem 5 The three charges shown below ( Q1 = 13.0 µc, Q2 = 13.0 µc, Q3 = 75.0 µc ) are at the corners of an isoceles triangle with sides a = 3.50 m and b = 2.00 m. 6 A Van de Graaf generator has a spherical metal ball on top, of radius r=31.0 cm. The electric field on the surface of the ball points outward, and its strength equals the breakdown field strength for air, E=\ensuremath{2.80\times 10ˆ{6}} V/m. a) What is the voltage at the surface of the metal ball? You are correct. Your receipt is b) Suppose a nitrogen molecule (mass \ensuremath{4.70\times 10ˆ{-23}}g) at the ball s surface loses an electron, so that it acquires a charge +e. What is its potential energy? You are correct. Your receipt is c) The nitrogen molecule is repelled by the generator and flies away. What is its velocity when it reaches a distance d=54.0 cm from the generator (measured from the centre of the sphere), if it starts near rest and doesn t bump into anything along the way? You are correct. Your receipt is Problem 7 Two large parallel plates having charges of equal magnitude but opposite sign are separated by 12.6 cm. Each plate has a surface charge density of 36.5 nc/m2. A proton is released from rest at the positive plate. a) Determine the potential difference between the plates. You are correct. Your receipt is b) Calculate the energy of the proton when it reaches the negative plate. You are correct. Your receipt is c) Calculate the speed of the proton just before it strikes the negative plate. Calculate the amount of work required to assemble this system of charges, assuming they are brought in from infinity. You are correct. Your receipt is d) Calculate the acceleration of the proton. You are correct. Your receipt is e) Calculate the force on the proton. You are correct. Your receipt is You are correct. Your receipt is f) From the force, calculate the magnitude of the electric field. Problem 6 You are correct. Your receipt is

4 7 Problem Set End. You do not need to hit the Submit All button below this line if you have already clicked submit for each individual field. Printed from LON-CAPA c MSU Licensed under GNU General Public License 8

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