Magnetic Field Deflection: Why No Work Done?

In summary, the magnetic force on a moving charge is described by the formula F = qv X B, where v and B are vectors. The magnetic field deflects an electron beam but cannot do any work on it because the magnetic force on the beam is zero, the acceleration of the beam is zero, and the magnetic force is perpendicular to the trace of the beam. It is also important to recall the properties of cross products of vectors.
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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
 
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What formula describes the magnetic force on a moving charge?
 
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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.
 
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  • #4
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.
 
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What do you think "trace of the beam" means? How does that relate to velocity?
 
  • #6
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..?
 
  • #7
Ok I see, thanks you guys.
 

1. What is magnetic field deflection?

Magnetic field deflection is the phenomenon in which a magnetic field causes a charged particle to change its direction of motion.

2. How does magnetic field deflection occur?

Magnetic field deflection occurs due to the interaction between the magnetic field and the charged particle's electric field. The magnetic force exerted on the particle causes it to change its direction of motion.

3. Why isn't any work done when a magnetic field deflects a charged particle?

No work is done because the magnetic force is always perpendicular to the direction of motion of the charged particle. As a result, the force does not cause any displacement, and work is equal to zero.

4. Can a magnetic field deflect any charged particle?

Yes, a magnetic field can deflect any charged particle, regardless of its mass or charge. The extent of deflection depends on the strength of the magnetic field and the velocity of the particle.

5. What are the applications of magnetic field deflection?

Magnetic field deflection is used in various applications such as particle accelerators, mass spectrometers, and cathode ray tubes. It is also utilized in the study of charged particles in space and in medical imaging techniques such as magnetic resonance imaging (MRI).

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