22.14. An electron moving with a speed of 4.8×10 5 m/s in the positive x directi
ID: 1591024 • Letter: 2
Question
22.14. An electron moving with a speed of 4.8×105 m/s in the positive x direction experiences zero magnetic force. When it moves in the positive y direction, it experiences a force of 2.1×1013 N that points in the negative z direction.
Find the components of the magnetic field.(Express your answer using two significant figures. Enter your answers numerically separated by commas.)
22.28. IP An alpha particle (the nucleus of a helium atom) consists of two protons and two neutrons, and has a mass of 6.64×1027kg. A horizontal beam of alpha particles is injected with a speed of 1.3×105m/s into a region with a vertical magnetic field of magnitude 0.145 T .
a) How long does it take for an alpha particle to move halfway through a complete circle?
b) If the speed of the alpha particle is doubled, does the time found in part A increase, decrease, or stay the same?
c) Repeat part A for alpha particles with a speed of 2.6×105m/s.
Explanation / Answer
22.14)
Fb = q*(vxB)
Fb = -2.1*10^-3 k
v = 4.8*10^5 i
B = Bxi + Byj
vxB = 4.8*10^5*By k
Fb = q*(vxB)
-2.1*10^-13 k = 1.6*10^-19*4.8*10^5*By k
By = -2.7 T <<------answer
22.28)
In the magnetic field
Fb = Fc
q*v*B = m*v^2/r
r = mv/qB
Time t = pir/v = (2*pi*m)/qB
t = (pi*6.64*10^-27)/(2*1.6*10^-19*0.145)
t = 4.5*10^-7 s
(b)
stays same
(c)
t = (pi*6.64*10^-27)/(2*1.6*10^-19*0.145) = 4.5*10^-7 s
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