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

Click For Summary
SUMMARY

The discussion focuses on determining the magnitude and direction of an electric field (E) necessary to cancel the magnetic force acting on an electron moving with velocity (v) in a magnetic field (B). The relevant equations are F=qE for the electric force and F=qvB for the magnetic force. To achieve equilibrium, the electric field must be set equal to the magnetic force, leading to the equation E=vB. However, due to the negative charge of the electron, the electric field must be directed opposite to the velocity of the electron to effectively cancel the magnetic force and allow the electron to travel in a straight path.

PREREQUISITES
  • Understanding of electric fields and magnetic fields
  • Familiarity with the Lorentz force law
  • Knowledge of vector mathematics
  • Basic principles of electromagnetism
NEXT STEPS
  • Study the vector form of the Lorentz force equation
  • Learn about the right-hand rule for determining the direction of forces in magnetic fields
  • Explore the concept of electromagnetic induction
  • Investigate the behavior of charged particles in electric and magnetic fields
USEFUL FOR

Students and professionals in physics, particularly those focusing on electromagnetism, as well as educators teaching concepts related to electric and magnetic forces on charged particles.

jakeowens
Messages
34
Reaction score
0
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?
 
Physics news on Phys.org
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
 

Similar threads

Making sense of sequence of ideas in MIT OCW's 8.02 notes on Faraday
  • · Replies 1 ·
Replies
1
Views
2K
Induced current and force on circular loop in varying magnetic field
  • · Replies 4 ·
Replies
4
Views
1K
Magnetic field due to electric wire
  • · Replies 6 ·
Replies
6
Views
1K
Determine the force with which the magnetic field of a coil acts on an infinitesimal cube of iron
  • · Replies 6 ·
Replies
6
Views
1K
What is the induced magnetic force on this closed current loop?
  • · Replies 12 ·
Replies
12
Views
2K
Electron passing through a magnetic and an electric field
  • · Replies 2 ·
Replies
2
Views
2K
Why is magnetic field B along a straight wire circular not radial?
  • · Replies 14 ·
Replies
14
Views
3K
Velocity along the cylinder axis
  • · Replies 18 ·
Replies
18
Views
2K
Electric and Magnetic field acting on an electron
  • · Replies 25 ·
Replies
25
Views
5K
Electric field in a rotating rod in a magnetic field
  • · Replies 3 ·
Replies
3
Views
2K