Magnetic fields

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A Fe+ ion is traveling at 200 m/sec in a direction 20 deg south of west at a point. The magnetic field at that point is 0.4 T directed at 10 deg west of south. What is the instantaneous magnetic force that acts on the Fe is how many newtons?
 

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  • #2
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The magnetic force on a charge that travels through a magnetic field is:
[tex]\vec F_m = q\vec V \times \vec B = q|V||B|\sin \alpha[/tex]
([itex]\alpha[/tex] being the angle between the field vector and the velocity vector of course.)
 
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  • #3
ZapperZ
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Originally posted by Chen
The magnetic force on a charge that travels through a magnetic field is:
[tex]\vec F_m = q\vec B \times \vec V = q|B||V|\sin \alpha[/tex]
([itex]\alpha[/tex] being the angle between the field vector and the velocity vector of course.)
I normally would not be picky on such things. However, it should be corrected that the general form of Lorentz force for the magnetic field term is proportional to q(v x B), not q(B x v).

Since the original question involves the exact vectorial direction of the force, and since cross products are not commutative, this can produce an error in the direction.

Zz.
 
  • #4
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Of course, I've corrected my post. Thanks for pointing my mistake out. :smile: Usually I just use the right-hand rule to find the direction of the magnetic force.
 

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