2015 AP Physics C物理C—Electricity and Magnetism电磁真题系列之简答题免费下载

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2015 AP Physics C Electricity&Magnetism Free-Response Questions Free Download

2015 AP 物理C电磁简答题部分免费下载

此套题仅 p II含有简答题，

共计时45分钟，共3题

占总分50%

每道大题可能含有不同数量的小题

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部分真题预览：

1）A parallel-plate capacitor is constructed of two parallel metal plates, each with area A and separated by a distance D. The plates of the capacitor are each given a charge of magnitude Q, as shown in the figure above.Ignore edge effects.

1. 1. On the figure above, draw an arrow to indicate the direction of the electric field between the plates.
   2. On the figure above, draw an appropriate Gaussian surface that will be used to derive an expression for the magnitude of the electric field E between the plates.
   3. Using Gauss’s law and the Gaussian surface from part (a)-ii, derive an expression for the magnitude of the electric field E between the plates. Express your answer in terms of A, D, Q, and physical constants, as appropriate.
      
      The space between the plates is now filled with a dielectric material that is engineered so that its dielectric constant varies with the distance from the bottom plate to the top plate, defined by the x-axis indicated in the diagram above. As a result, the electric field between the plates is given by , where κ₀ is a positive constant. Express all algebraic answers to the remaining parts in terms of A, D, Q, κ₀, x, and physical constants, as appropriate.
2. Determine an expression for the dielectric constant k as a function of x.
3. 1. Write, but do NOT solve, an equation that could be used to determine the potential difference V between the plates of the capacitor.
   2. Using the equation from part (c)-i, derive an expression for the potential difference V_D - V₀, where V_D is the potential of the top plate and V₀ is the potential of the bottom plate.
4. Determine the capacitance of the capacitor.
5. The energy stored in the capacitor that has a varying dielectric is U_v . A second capacitor that has a constant dielectric of value κ₀ is also given a charge Q. The energy stored in the second capacitor is U_C . How do the values of U_v and U_C compare?
   ______U_v<U_C______U_v>U_C_____U_v=U_C
   Justify your answer.