「每日一练」 IB物理例题解析及练习Capacitor

「每日一练IB Physics」

今日知识点：Capacitor

例题

A capacitor of capacitance C discharges through a resistor of resistance R. The graph shows the variation with time t of the voltage V across the capacitor.

The capacitor is changed to one of value 2C and the resistor is changed to one of value 2R. Which graph shows the variation with t of V when the new combination is discharged?

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解析

此题考察的是discharge circuit中potential difference, V和time, t的关系。实际上，Q, V, I都与t有着十分类似的关系，可以一起记下来。

where time constant, τ=RC

而本题中，R与C都增加了两倍，independent variable与原先相比减小到1/4，由数学中Transformation的知识可以得出，graph experiences horizontal stretch by a factor of 4，故选项B为正解。

下面翰林小助手为大家准备了一道同类型的题目，请大家一起来试试解答。

Your turn

A fully charged capacitor is connected to a resistor. When the switch is closed the capacitor will discharge through the resistor.

Which graphs correctly show how the charge on the capacitor and the current in the circuit vary with time during the discharging of the capacitor?

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Correct Answer：A