I.) Planar motion: An electron enters a magnetic field of 0.4 T, moving perpendi
ID: 1454751 • Letter: I
Question
I.) Planar motion: An electron enters a magnetic field of 0.4 T, moving perpendicular to it with a speed of 7·105 m/s.
a.) Find the radius of the orbit it will make. 9.96 Correct: Your answer is correct. . µm
b.) If the magnetic field points directly away from you (into the page), then this orbit would be in which direction from your perspective? clockwise Correct: Your answer is correct. .
II.) Helical motion: If an electron were sent at the same speed, but at an angle of 70o to the magnetic field:
c.) What would be the radius of the helical motion? 10.6 Incorrect: Your answer is incorrect. . µm
d.) How long would it take for the electron to travel 3 m along ("downstream" to) the magnetic field? (No Response) µs e.)
In general, will an electron need to always travel in the same direction as ("downstream" to) the magnetic field? (No Response)
Explanation / Answer
II) Helical motion:
when a charged particl enters the magnetic filed at an angle , the speed component that is perpendicular to the magnetic field make it circular motion where is component parallel to the field has no impact of the field and cuases liner motion of the particle along the field resulting a helical motion of the particle.
speed v= 7e+5 m/s
particle makes angle 70 deg with the field
perpendicular component vp = 7.0e+5 Sin(70) = 6.58e+5 m/s
horizontal component vh = 7.0e+5 Cos(70) = 2.39e+5 m/s
radius of the helix R = mv/Bq = 9.0e-31*6.58e+5/(0.4*1.6e-19) = 9.25e-6 m
horizontal speed = 2.39e+5 m/s
distance to travel = 3 m
time to travel = 3/2.39e+5 = 12.55e-6 s
The electron may travel upstream or downstream wrt to the magnetic field dependign on the horizontal component of the velocity at entry. It will take the direction of the horizontal component.