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Thompson’s Apparatus

This is probably the best experiment I have to demonstrate that electrons are particles.

Your students could draw a free-body force diagram to show the electric and magnetic forces on the electrons and perhaps even work through the algebra to find he charge to mass ratio themselves.

The final path taken by the electrons is not flat. This is because the electric field causes the electron to follow a parabolic path while the magnetic field causes it to follow a circular path over the same distance and the two together give the path as observed.

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