Determining Electric and Magnetic Fields: An Electron's Journey

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Homework Help Overview

The problem involves determining the magnetic field associated with an electron moving in a uniform electric and magnetic field, given its velocity, acceleration, and the electric field's magnitude. The context is rooted in electromagnetism, specifically the interaction of charged particles with electric and magnetic fields.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the need to apply Newton's second law and the force equation involving electric and magnetic fields. Questions arise regarding the implications of the velocity and field directions, particularly concerning the x-component of the magnetic field.

Discussion Status

The discussion is active, with participants providing insights into the application of relevant physics principles. There is a focus on understanding the relationship between the directions of velocity and fields, particularly in the context of vector cross products.

Contextual Notes

Participants note the importance of the mass of the electron and the challenge of determining the magnetic field's characteristics based on the given information. There is an acknowledgment of the limitations in determining certain aspects of the magnetic field due to the nature of vector operations.

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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?

Homework Equations



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.
 
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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.
 

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