# Speed of electron into electric/magnetic fields

• shanktank
In summary, the conversation is discussing the calculation of the speed of an electron as it enters an electric and magnetic field. The given values are V = 2000 V, d = 0.080 m, and B = 0.0028 T. The goal is to find the speed at which the electron passes through both fields undeflected. The attempt at an answer includes using the equations E = F/d and F = Bqv to calculate the electric field and force, but the magnetic field is not accounted for. The conversation ends with the suggestion to finish the calculation to find the correct answer.

#### shanktank

attached is my attempt to answer part b) of this question. I have been told its wrong but don't know what I'm missing, any ideas?

#### Attachments

• physics 30.jpg
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sorry the image didn't show up like planned i'll type it out.

b) Calculate the speed of the electron moving into the electric and magnetic fields...

we have a diagram in part a) that shows an electron moving into the plane of the page.

were given:
V = 2000 V between charged plates
d= 0.080 m between charged plates
B = 0.0028 T

The electron enters the electric field, which is perpendicular to the magnetic field, and passes through both fields undeflected.

Here now is my attempt at an answer.

V=2000 V
d= 0.080 m
B = 0.0028 T
q = 1.60 x 10^-19 C

E = F/d E = 2000 V / 0.080 m = 25000 V/m

F= Bqvelocity

F= Eq
(25000V/m)(1.60 x 10^-19)
= 4 x 10^-15 N

I can't see the image yet, so correct me if I'm wrong about what's going on.

What have you done with the magnetic field in your calculation? If the electron passes undeflected, that means the force from the electric field and the force from the magnetic field must cancel out. So at what speed does that happen? I think you have started out OK, you just need to finish. Why is your work considered wrong?

## 1. What is the speed of an electron in an electric field?

The speed of an electron in an electric field can vary depending on the strength of the field and the initial velocity of the electron. However, in a constant electric field, the speed of an electron can be calculated using the equation v = E/m, where v is the speed, E is the electric field strength, and m is the mass of the electron.

## 2. Does the speed of an electron change in a magnetic field?

Yes, the speed of an electron can change in a magnetic field. This is because a magnetic field exerts a force on a moving charged particle, causing it to accelerate. The speed and direction of the electron's motion can be calculated using the Lorentz force equation F = qvB, where F is the force, q is the charge of the electron, v is the velocity, and B is the magnetic field strength.

## 3. What factors affect the speed of an electron in an electric/magnetic field?

The speed of an electron in an electric/magnetic field is affected by the strength of the field, the initial velocity of the electron, and the mass and charge of the electron. Additionally, external factors such as temperature and other particles in the field can also affect the speed of the electron.

## 4. Can the speed of an electron exceed the speed of light in an electric/magnetic field?

No, the speed of an electron cannot exceed the speed of light in any field. According to Einstein's theory of relativity, the speed of light is the maximum speed at which anything can travel in the universe. Therefore, the speed of an electron in an electric/magnetic field can never exceed the speed of light.

## 5. How does the speed of an electron in an electric/magnetic field affect its behavior?

The speed of an electron in an electric/magnetic field can affect its behavior in various ways. For example, the speed of an electron determines the amount of energy it carries, which can impact its interactions with other particles in the field. Additionally, the speed of an electron can affect its trajectory and the strength of its magnetic field, which can have implications for its overall behavior in the field.