2014年AP电磁学简答题真题+答案+PDF下载
E&M. 1.
Physics students are analyzing the circuit above. A variable DC power supply is connected to an ammeter and three resistors. The resistances of two of the resistors are known to be R2=R3=50Ω, but the resistance of the third resistor is unknown. The students collect data on the potential difference across the power supply and the current measured by the ammeter, as follows.
(a) On the grid below, plot the data points for the current as a function of the potential difference. Clearly scale and label all axes, including units if appropriate. Draw a straight line that best represents the data.
(b) Using the straight line from part (a), calculate the total resistance of the three-resistor combination.
(c) Calculate the value of R1.
The power supply is now fixed at 12 V.
(d) Calculate the current through R2
(e) Resistor 3 is now removed and replaced by an open switch in series with an uncharged 4 nF capacitor, as shown below. The power supply is still fixed at 12 V.
i. Calculate the current in R2 immediately after the switch is closed.
ii. A long time after the switch is closed, will the magnitude of the current in r2 be greater than, less than, or equal to the current through R2 found in part (d) ?
_____Greater than _____Less than _____Equal to
Justify your answer.
(f) The 4 nF capacitor is replaced with an uncharged 10 nF capacitor. Will the magnitude of the current in R2 immediately after the switch is closed be greater than, less than, or equal to the current in part (e)i ?
_____Greater than _____Less than _____Equal to
Justify your answer.
2014年AP电磁学简答题真题余下省略！
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