Question

Solve problem 2 and 3 with details . Thank you

Notre Dame University-Louaize Faculty of Natural& Applied Sciences Department of Physics& Astronomy PHS 212-Electridity & Magnetism Fall 2018 Final Exam (22Dec18, 120min) Closed-book, Closed-notes, Close-everything Exam List in detail any assumptions that you make. Show all your work. You can use a calcalater Useful Constants: e1.6x 10C, charge of 1 electron k-8.9875x10 Nm/C2 mass of 1 electron: 9.11 x 10 kg 1. Three point charges, q +15 C, q +35 HC, and q3--35 uC, are arranged on an x-y axis as shown in the figure. The distance between charges q, and q, is 25 cm and the distance between charges q and 92 25 cm q, is 25 cm. Where could you locate a fourth point charge, q +55 pC, such that the net electrostatic force on q, is zero? Express your answer in terms of the distance from charge q, and an angle measured from the x-axis 91 25 cm 9a 2 An infinitely long cylindrical insulating shell of inner radius a and outer radius b has a uniform volume charge density p (C/m'). A line of charge density À (C/m) is placed along the axis of the shell. Determine the electric field intensity at (a) rca, (b) acrcb (c)r>b. 3) The figure below shows four solid non-conducting spheres, each with charge Q uniformly distributed throughout its volume. (a) Derive the charge density for every sphere and then rank them according to their volume charge density, greatest first. e figure also shows a point P for each sphere, all at the same distance from the center of the sphere. (b) Now assume that the four spheres are conducting (and each has charge Q. Calculate the electric fields at point P and rank the spheres according to the magnitude of the electric field they produce at point P, greatest first. Page 1 4, A copper wire ( 1.75 x 10"Qm) of cross-sectional area A-1.35 x 10" ㎡ and length L - 6.5 m is connected to a 10 V power supply. What is (a) the current in the wire, (b) the magnitude of the current density, (c) the magnitude of the electric field in the wire, and (d) the rate at which thermal energy is dissipated by the wire? (e) For each of the following changes, does the electron drift speed increase, decrease, or remain the same? (of course, support your claim by equations) i) increasing V (A and L constant) ii) increasing L, (V.and A constant) ii) decreasing A, (V and L constant) 5. In the figure, what is the net electric potential at the origin (assuming V - 0 at infinity) due to the circular arc of charge +Q (whose center of +2 2R 20炉 curvature is at the origin and the two particles of charges +4Q and -2Q? Let Q- 8 uC and R 1.5 m. 6. The figure shows the path of an electron that passes through two regions containing uniform magnetic fields of magnitudes Bi and B2. Its path in each region is a half-circle. (a) Calculate the magnitudes of Bi and B2 and note which field is stronger (b) What is the direction of B,? What is the direction of B2? (c) Calculate the time spent By by an electron in region 1. Calculate the time spent by an electron in region 2. Which is bigger? Page 2

Answer 1

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