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Unformatted text preview: Physics 21 Fall, 2008 Hour Exam #2 1 2 3 4 5 Total Name: Recitation Time Recitation Leader November 4, 2008 This exam is closed notes and closed book. You must show enough work on each problem to convince the grader you understand how to solve the problem. You may use a calculator, but show every number that you use to get numerical results. The penalty for arithmetic errors is small if the grader can tell what you intended to do. Give units for all final answers. There is an equation sheet on the last page. All problems count 20 points. Problem 1. For the following circuit (a) (5 pts.) Write the loop equation for this circuit. (b) (5 pts.) Write the expression for the phase an- gle φ of this circuit in terms of R , L , C , and the frequency ω of the ac power supply. (c) (5 pts.) If R = 12 . 0 Ω, L = 90 . 0 mH, C = 50 . µ F, and ω = 120 π rad / s, draw a phasor di- agram for this circuit that is approximately to scale. Include a phasor for the ac voltage V , and give the length of each phasor. Find the peak value of the current I if the peak voltage supplied by the power supply is 8 . 00 V. (d) (5 pts.) For the parameters given in part (c), find the phase angle φ and the average power delivered to the circuit by the power supply. Problem 2. A long wire lies in the xy plane and car- ries a 3.0 A current as shown in the diagram. The thick segment centered at the origin has a length 3.0 mm and makes an angle of 30 ◦ with the x axis. x y I 30 Find the magnetic field at the following points due to the thick segment of the wire centered at the origin....
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- Spring '07