# 2049H Exam1 - 2049H Exam #1        Name:   ...

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Unformatted text preview: 2049H Exam #1        Name:                                                                                    Problem 1 [44 pts]    Uniformly Charged Solid Sphere (note it is not metallic) has radius R and volume  charge density ρ.      Calculate electric field (its dependence on  r)  (a) for outside the sphere [8 pts]  (b) for inside the sphere [8 pts]    Calculate potential (its dependence on r)  (c) for outside the sphere [12 pts]  (d) for inside the sphere [12 pts]    (e) Does potential vary inside the  sphere?  [4 pts]                                                                Problem 2 [44 pts]  Parallel plate capacitor is charged to area charge  density as depicted.  You can assume that the area of  the capacitor is A and the distance between capacitor  is d.    (a) What is the electric field between the plates?  [4 pts]  (b) What is the voltage difference between plates?   Which plate has the positive voltage? [4 pts]  (c) What is the force between the plates? [proceed  carefully.  Ask what is the electric field by one  plate first before doing the superposition] [12  pts]  (d) How much work does it take to move the plate  on the left further away from the other plate  by distance d? [12 pts]  (e) What is the energy stored in the original  configuration?  You can assume that you need to move the plate from  distance 0 to d.  Answer in terms of Q (σ×A), and C (capacitance) [12 pts]                                                Problem 3 [True or False Questions] [12pts]  Dielecric strength (maximum electric field) of air is 3×106 V/m.       (a) Given a parallel plate capacitor, maximum charge per unit area you can store  depends on the separation between two plates. [3 pts]        (b) If you have large spherical metallic shell and small spherical shell, you can  store more charge on larger shell. [3 pts]          (c) If you have two capacitors (with equal capacitance) in series, the total  capacitance is larger than that of each capacitor. [3 pts]            (d) Energy of 500 eV is equivalent to an electron being accelerated through a  potential difference of 500 volts.  It does not matter how the potential is  being applied. [3 pts]        ...
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## This note was uploaded on 07/16/2011 for the course PHY 2049H taught by Professor Staff during the Spring '09 term at University of Central Florida.

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