Question

Given your understanding of how the e/m apparatus works, what should happen to the radius of the electron beam when the current is increased/decreased at constant voltage? What should happen to the radius of the electron beam when the voltage is increased/decreased at constant current? Explain.

Answer 1

In the experiment, the followings formulas are used:

where v is the velocity of the electron/charge.

where V is the accelerating voltage.

If the current is increased at a constant voltage it means that the no. of electrons are increased. But the velocity is same. Hence, the radius of the electron beam will be same.

If the accelerating voltage is increased, it will result in increased KE. Hence increased velocity. Therefore, the radius will also increase (look at the 3rd formula).