How Does an Electric Field Cancel Out Magnetic Force on an Electron?

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Homework Help Overview

The discussion revolves around the interaction between electric and magnetic fields, specifically how an electric field can cancel the magnetic force acting on an electron traveling in a magnetic field. The subject area includes electromagnetism and the forces on charged particles.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between electric and magnetic forces, questioning the conditions under which they can cancel each other. There are attempts to derive the necessary electric field magnitude and direction, with some participants expressing confusion about the vector nature of the forces involved.

Discussion Status

The discussion is active, with participants providing guidance on the need for vector forms of the equations and the importance of directionality in the forces. There is an acknowledgment of the complexity involved in determining the correct directions of the electric and magnetic fields.

Contextual Notes

Some participants note the lack of specific information provided in the problem statement, which contributes to confusion regarding the directions of the forces and fields. There is also a reminder to consider the charge of the electron when determining the direction of the electric field.

jakeowens
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What magnitude and direction would an electric field, E, need to be to cancel out the force on an electron traveling with speed, v, in magnetic field B?

I know the formula for the force on an electron in a magnetic field is F=qvB. The formula for the force on an electron in a electric field is F=qE. can i just set the two equal to each other? giving me qE=qvB, divide by q, giving me E=vB? is that right?
 
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Your answer is supposed to have magnitude and direction, so you need to use the vector forms of the equations that you list. Other than that, you are on the right track. BTW, what is the shape of the path of an electron moving with velocity v in a magnetic field? When you get your E(t) field correct, the electron will go back to just a straight path with velocity v.
 
I don't know any information other then what was given, that's why I'm slightly confused, I am just getting messed up in the directions
 
The electric field has to flow in a direction (from positive to negative) in the same direction as the force from the magnetic field correct? that way the electron will be attracted back, canceling out the force from the magnetic field, allowing it to travel in a straight path. Am i right?
 
jakeowens said:
The electric field has to flow in a direction (from positive to negative) in the same direction as the force from the magnetic field correct? that way the electron will be attracted back, canceling out the force from the magnetic field, allowing it to travel in a straight path. Am i right?

Actually because the electron has a negative charge, the electric field will point in the direction opposite to the direction of the velocity. I think what the question is after is the relative directions of the vectors involved, so sketch a quick diagram and make an assumption of what direction the E field is, then figure out the required direction of B.

Note: The magnetic force is NOT F=qvB. Use the vector version of this equation!

-Dan
 

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