今日知识点：Magnetic Force

例题

Q: A proton p and an electron e, with the same velocity, enter a magnetic field which is perpendicular to the direction of their motion. The field acts into the page. Which of the following diagrams best represents the motion of the particles?

解析

首先利用Fleming‘s Left Hand Rule来判断受力方向，注意的是电流方向与positive charge一致，与electron方向相反，因此排除AB，答案在CD中。其次需要注意的是proton和electron的charge绝对值一样，但electron mass较轻，因此偏转较为明显，故选择C。

下面我们为大家准备了一道同类型的题目，请大家一起来试试解答。

The photograph shows particle tracks from a particle detector.

Two new particles are created at point X. The tracks of the new particles are labelled Y and Z.

A. The magnetic field acts into the page.

B. The new particles are an electron and a positron.

C. The new particles have opposite charge.

D. The particle at Y is positively charged.

（答案请见下方）

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Correct Answer: C