Magnetic Field Deflection: Why No Work Done?

AI Thread Summary
A magnetic field can deflect an electron beam without doing work because the magnetic force acts perpendicular to the velocity of the beam, resulting in no work being done. The formula for the magnetic force on a moving charge is F = qv X B, emphasizing that the force is a vector cross product. The discussion highlights the misconception that the magnetic force could be zero or that the acceleration of the beam is zero, which is incorrect. Clarifications about the "trace of the beam" suggest it relates to the beam's velocity and direction. Ultimately, the key takeaway is that the perpendicular nature of the magnetic force to the motion of the beam prevents work from being done.
artupayam
Messages
3
Reaction score
0
A magnetic field deflects an electron beam, but it can not do any work on the beam. Why?

a. since the magnetic force on the beam is zero
b. since the acceleration of the beam is zero
c. since the magnetic force is perpendicular to the trace of the beam
d. none of them
 
Physics news on Phys.org
What formula describes the magnetic force on a moving charge?
 
Recall that the formula for a force of a magnetic field on a charged particle is given by:

F = qv X B , where v and B are vectors.

Also recall the properties of cross products of vectors.
 
Last edited:
Wrong Answer

Initially I chose d. since the magnetic force is perpendicular to the velocity of the beam. But it was the wrong answer so I took it off from the choices.
 
What do you think "trace of the beam" means? How does that relate to velocity?
 
Artupayam, it seems to me you were thinking along the right lines ... not sure why that didn't lead you to the right answer.

You should be able to eliminate 2 more by default. So only possible answer is..?
 
Ok I see, thanks you guys.
 

Similar threads

Induced current and force on circular loop in varying magnetic field
Replies
4
Views
964
Direction of the magnetic needle
Replies
11
Views
2K
Understanding work in translation and rotation of a magnetic dipole
Replies
1
Views
2K
Moving charge deflected by a loop of wire
Replies
1
Views
655
What is the magnetic field generated by these two particle beams?
Replies
14
Views
2K
Determine the force with which the magnetic field of a coil acts on an infinitesimal cube of iron
Replies
6
Views
908
Magnetic field pointing into a normal magnetized compass needle
Replies
16
Views
1K
Why does a diamagnetic rod align perpendicular to a magnetic field?
Replies
8
Views
2K
I Charge movement relative to magnetic field frame dependence/invariance
Replies
5
Views
850
Angle of deviation from a magnetic field
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top