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

In summary, the conversation discusses the necessary magnitude and direction of an electric field, E, to cancel out the force on an electron traveling with speed, v, in a magnetic field, B. To find the correct direction, the vector forms of the equations for the force on an electron in a magnetic field (F=qvB) and an electric field (F=qE) must be used. The electric field must flow in the opposite direction of the electron's velocity to cancel out the force from the magnetic field. A diagram and assumptions may be helpful in determining the required direction of the electric field.
  • #1
jakeowens
34
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?
 
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  • #2
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.
 
  • #3
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
 
  • #4
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?
 
  • #5
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
 

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

What is a magnetic field?

A magnetic field is a physical phenomenon that is produced by moving electrical charges, such as electrons. It is a force field that can be felt by other moving electrical charges and can exert a force on them.

How are magnetic fields created?

Magnetic fields are created by the movement of electrical charges, either through the movement of electrons or the flow of electricity. They can also be created by permanent magnets or electromagnets.

How do magnetic fields affect electrons?

Magnetic fields can exert a force on electrons, causing them to move in a circular pattern around the magnetic field lines. This is known as the Lorentz force and is the basis for many devices, such as motors and generators.

Can magnetic fields be shielded or blocked?

Yes, magnetic fields can be shielded or blocked by materials that are not affected by magnetic fields, such as lead or certain types of alloys. This is why some electronic devices are encased in metal to protect them from outside magnetic interference.

How are magnetic fields used in everyday life?

Magnetic fields have many practical applications in everyday life, such as in motors, generators, and speakers. They are also used in medical imaging devices, such as MRI machines, and in credit cards and hotel key cards for data storage.

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