# Velocity Selectors: Why Opposite Direction?

• v_pino
This electric field will cause the electrons to move in opposite directions, depending on their charge. This can be explained by the Lorentz force law, which states that the force on a charged particle moving through a magnetic field is proportional to the charge of the particle, the velocity of the particle, and the strength of the magnetic field. In summary, the movement of electrons in opposite directions in the velocity selector can be attributed to the combination of the electric and magnetic fields present.
v_pino
I understand that fast electrons will experience a larger force from the magnetic field and slower electrons will experience a smaller force. But how come they will move in opposite directions?

v_pino said:
I understand that fast electrons will experience a larger force from the magnetic field and slower electrons will experience a smaller force. But how come they will move in opposite directions?

What "opposite directions"? Please show where you got this. Use the Lorentz force law.

Zz.

here is the image of a section of the velocity selector

thanks

v_pino said:
here is the image of a section of the velocity selector

thanks

I guess this makes sense, because an electron is too small to see with the naked eye.

{ZapperZ smacks himself silly}

Zz.

LOL

v_pino said:
I understand that fast electrons will experience a larger force from the magnetic field and slower electrons will experience a smaller force. But how come they will move in opposite directions?
The velocity selector also has an electric field.

## 1. What is a velocity selector?

A velocity selector is a device used in physics experiments to select particles with a specific velocity. It consists of two charged plates placed perpendicular to the direction of motion of the particles and a uniform magnetic field.

## 2. How does a velocity selector work?

A velocity selector works by using the electric and magnetic fields to exert forces on the charged particles. The electric field causes the particles to accelerate, while the magnetic field causes them to deflect. By adjusting the strength and direction of the fields, only particles with a specific velocity will pass through the selector.

## 3. Why are the plates in a velocity selector placed perpendicular to the magnetic field?

The plates are placed perpendicular to the magnetic field to ensure that the magnetic force on the particles is always perpendicular to the electric force. This allows for the particles to experience a net force in the direction of their initial velocity, which is necessary for the selector to work effectively.

## 4. What happens to particles with velocities that do not match the selector's setting?

Particles with velocities outside of the selector's setting will either be deflected away from the direction of motion or accelerated towards the plates. This results in the particles not passing through the selector and being filtered out of the experiment.

## 5. Why are opposite directions used in a velocity selector?

Opposite directions are used in a velocity selector to ensure that the force on the particles is always perpendicular to their initial velocity. This allows for precise selection of particles with a specific velocity, which is crucial in many physics experiments.

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