Download Physics 208 Exam 2: Electricity and Magnetism and more Exams Optics in PDF only on Docsity! Physics 208: Electricity and Magnetism. Exam 3, Secs. 501–505 13 April 2006 Instructor: Dr. George R. Welch, 301D Doherty Bldg, 845-1571 Print your name neatly: Last name: First name: Sign your name: Please fill in your Student ID number (UIN): – – IMPORTANT Read these directions carefully: • There are 7 problems totalling 100 points. Check your exam to make sure you have all the pages. Work each problem on the page the problem is on. You may use the back. If you need extra pages, I have plenty up front. • Indicate what you are doing! We cannot give full credit for merely writing down the answer. Neatness counts! I will give generous partial credit if I can tell that you are on the right track. This means you must be neat and organized. • Each problem with its associated figure is self explanatory. If you must ask a question, then come to the front, being as discrete as possible so as not to disturb others. • Put your name on each page it is asked for. You will lose credit if you fail to print your name on each page it is asked for. Print your name: Physics 208: Electricity and Magnetism, Exam 2 Problem 1. 15 points. There is a uniform magnetic field B (pointing into the page) through a large rectangular region of space. A wire carrying current I goes a distance a directly into the region of field, then bends and comes back out at an angle θ from its original direction. Find the x and y components of the force on the wire. Express your answers in terms of B, I, l, θ, and numerical factors. Magnetic Field B (into the page) θ RV I I a Be neat. Neatness helps. Work neatly. Print your name: Physics 208: Electricity and Magnetism, Exam 2 Problem 4. (20 points) A long straight wire carries a changing current i(t). A rectangular loop of wire is placed near the long straight wire. The loop is made of a resistive material and the total resistance of the loop is R. The distance from the long straight wire to the near edge of the loop is c, and the width and height of the loop are a and b respectively. All these dimensions (a, b, and c) are much smaller than the length of the long straight wire. The situation is shown in the Figure. i(t) b c a Suppose that the current in the long straight wire var- ries according to i(t) = I0 ( 1− t τ ) 0 < t < τ 0 t > τ Calculate the magnitude and direction (clockwise or counter-clockwise) of the current induced in the loop, for 0 < t < τ . Work neatly! If you are neat, I can read what you did and maybe find more points for you. Print your name: Physics 208: Electricity and Magnetism, Exam 2 Problem 5. (10 points) For each of the following 5 cases (a)–(e) there is a loop of wire denoted A near another wire that is conducting some current. In each case, current is induced in loop A. Indicate whether the induced current is clockwise or counter-clockwise. Please only write either “clockwise” or “counter-clockwise” as the answer for each case. Points: 5 correct = 10 points, 4 correct = 7 points, 3 correct = 3 points. I increasing A Answer: I decreasing (a) (b) A Answer: (c) Answer:I increasing I increasing A A Answer: Answer: (d) (e) I constant Loop moving to right A Print your name: Physics 208: Electricity and Magnetism, Exam 2 Problem 6. (5 points) The following laws were found empirically and formed the basis for understanding the interaction of charges and currents. Gauss: ∮ ~E · d ~A = Qinside ²0∮ ~B · d ~A = 0 Ampère: ∮ ~B · d~l = µ0Ienclosed Faraday: ∮ ~E · d~l = − d dt ΦB Indicate which one of these laws Maxwell changed in advance of his prediction of electromagnetic waves, and write down the corrected version of that law. You should be neat. You are more likely to get it right if you work neatly.
