# Determining Electric and Magnetic Fields: An Electron's Journey

• dpeagler
In summary, in this conversation, the problem is discussed of finding the magnetic field in a region where an electron has a given velocity and acceleration in a uniform electric and magnetic field. The equation F = qE + qv x B is mentioned and it is noted that the mass of the electron can be looked up. It is also pointed out that Newton's second law needs to be used and that the x-component of the magnetic field would be zero when crossed with the velocity. However, the specific value for the magnetic field cannot be determined.
dpeagler

## Homework Statement

An electron has a velocity of 1.2 * 10^4 m/s ( in the positive x direction ), and an acceleration of 2 * 10 ^ 12 m/s^2 ( in the positive z direction ) in a uniform electric and magnetic field. If the electric field has a magnitude of 20 N/C ( in the positive z direction), what can you determind about the magnetic field in the region? what can you not determine?

F = qE + qv x B

## The Attempt at a Solution

I need the force quantity to figure out the problem, but am lost besides this. Can someone offer a little help. Thanks.

You are given the acceleration and the mass of an electron is something you can easily look up.

Ok I was thinking I was going to be using Newton's second law, but wan't sure. I have the answers to the problem and for the x- vector it says it can be any negative value, can anyone explain why this is?

Well you do need to use Newton's 2nd law since F = ma to use the left hand side of your equation. As far as the x-direction of the magnetic field is concerned, what happens when you cross a velocity, that is in the x-direction, with a field in the x-direction? Matter of fact, what happens when you cross any 2 parallel directions together?

It would be zero not any negative value correct?

Thanks for all of the help.

Yes, any x-component, negative or positive, crossed into the velocity would give 0 here.

## 1. What is the purpose of determining electric and magnetic fields in an electron's journey?

The purpose of determining electric and magnetic fields in an electron's journey is to understand the forces acting on the electron and how it will move through the field. This information can be used to predict the trajectory of the electron and its behavior in different environments.

## 2. How do electric and magnetic fields affect the path of an electron?

Electric fields exert a force on charged particles, causing them to accelerate in the direction of the field. Magnetic fields, on the other hand, exert a force perpendicular to the motion of the charged particle, causing it to move in a circular or helical path. The combination of these two fields can result in complex trajectories for electrons.

## 3. What techniques are used to determine electric and magnetic fields?

There are several techniques used to determine electric and magnetic fields, including using electric and magnetic field sensors, measuring the deflection of charged particles in the field, and using mathematical equations to calculate the fields based on known parameters.

## 4. What factors affect the strength of electric and magnetic fields?

The strength of an electric field is affected by the amount and distribution of charge, as well as the distance between the charges. The strength of a magnetic field is affected by the strength of the current, the distance from the current, and the orientation of the current with respect to the observer.

## 5. How are electric and magnetic fields related?

Electric and magnetic fields are related through Maxwell's equations, which describe the interactions between electric and magnetic fields. These equations show that a changing electric field can create a magnetic field, and a changing magnetic field can create an electric field. This relationship is essential in understanding the behavior of charged particles in electromagnetic fields.

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