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EE 151 Caltech Electromagnetic Engineering Spring ‘05 Homework 2 Due Tuesday, April 12thin class 1. (a)(1)The width of the region containing εR1in Fig. 1 is 1.2 m. Find εR1if εR2= 2.5 and the total capacitance is 60 nF. (2)Find the width of each region (containing εR1and εR2) if Ctotal= 80 nF, εR2= 3 εR1, and C1= 2 C2. (b)For the same system as in part (a), use Femlab to plot the E and D fields. Based on your simulation, answer the following questions: (1)At the interface of the two dielectric materials, is there any discontinuity of the E and D fields? Is there any net charge at the interface? (2)Which side of the capacitor has higher fringe field? (3)Taking into account the fringe fields, is the capacitance higher or lower than what you calculate in part (a)? Explain. 2 mεR12 mεR22 mmConducting plates Figure 1
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