Magnetic fields

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  • #1
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an electron with velocity u = (3,12,-4) x 10^5 experiences no net force at a point in a magnetic field B = ((10,20,30)/ Find E at that point.

I found the magnetic force by u cross B. Set Fe equal to Fm. Divided by q to get E = u cross B. but im not getting the same answer as the back of the book. just need a confirmation.
im getting E = (4.4 x 10^7, -1.3 x 10^7, -6 x 10^6)
the book has the same number for the x direction, its just 4400.
 
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  • #2
dextercioby
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[tex] m\vec{0}=q_{e}\left(\vec{E}+\vec{u}\times\vec{B}\right) [/tex]

That's all u need.Use it propertly.

Daniel.
 
  • #3
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I came up with the same numbers. It's just a simple cross product, the answers in the book must be wrong.
 
  • #4
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Signs should be reversed though, from bringing E to the other side of the Lorentz force equation.
 
  • #5
dextercioby
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Are u sure that [itex] E_{x} [/itex] is not [itex]-4.4\cdot 10^{7} \frac{V}{m} [/itex]...?

Daniel.
 
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  • #6
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what is that formula for?
 
  • #7
dextercioby
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What formula?

Daniel.
 

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