The earth\'s magnetic field can affect the electron beam in an oscilloscope or a

Question

The earth's magnetic field can affect the electron beam in an oscilloscope or a television tube. An electron that has been accelerated through a potential difference of 2.44 104 V has a horizontal initial velocity, directed north. Find the magnetic force on the electron when the earth's field has a horizontal component of 0.250 G and dips 60.0 degree below the horizontal (values typical in California). It is not 3.21e10-16 or 3.20*10-16, My professor said I need to do something with Bh=Bcos60(degrees).

Explanation / Answer

You have the formula but don't confuse velocity v with accelerating voltage V.
I get
q = (-)1.6021774E-19C
KE = qV = 1.6021774E-19 *2.44 10^4 = 3.91 x 10^-15 J
v = sqrt(2KE/m) = 2.2105 x 10^6 m/s
B = 0.0001*0.25 T

B along horizontal = B cos 60 = 0.5
F = qvB*sin(60 )cos(60) = 3.825E-18 N

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