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

历年AP Physics物理学系列

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

2015 AP 物理C电磁模考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

可以使用计算器

部分真题预览：

1）You perform a laboratory experiment to determine the unknown charge on a small conducting ball of mass m using the experimental setup shown in the diagram above. A variable power supply applies a DC voltage to two large parallel plates separated by a distance d, creating a uniform electric field. The charged ball hangs between the plates on an insulated thread of length L and is displaced from its lowest point, coming to equilibrium at an angle θ with the vertical. During the experiment, you measure the angle θ when the voltage indicated on the power supply is V .

1. On the dot below that represents the conducting ball, draw and label the forces (not components) that act on the conducting ball. Each force must be represented by a distinct arrow starting on, and pointing away from, the dot.
2. Derive an expression that would allow you to calculate the magnitude of the unknown charge on the ball given θ , V , m, d, L, and fundamental constants, as appropriate. If you need to draw anything other than what you have shown in part (a) to assist in your solution, use the space below. Do NOT add anything to the figure in part (a).
3. One way to determine a more accurate value for the magnitude of the charge on the conducting ball in the experiment is to perform multiple trials.
   1. What quantity would you vary in this experiment to obtain different values of the angle θ ?
   2. What quantities would you plot on a graph to obtain a linear relationship that can be used to determine the magnitude of the charge on the conducting ball?
4. Describe one difficulty in precisely and accurately determining the angle θ with a protractor, and describe a method to overcome the difficulty.
5. If the voltage is high enough, the ball touches one of the plates. Describe what happens from the time it touches until you turn off the voltage.