Charged particles from the Sun travel across space as a \"solar wind\". Some of
ID: 1631270 • Letter: C
Question
Charged particles from the Sun travel across space as a "solar wind". Some of them can penetrate Earth's ionosphere above the North Pole and produce beautiful light displays called Aurora borealis. Consider electrons, (charge q = 1.60 times 10^19 C and mass m = 9.11 times 10^31 Kg) that travel horizontally with a kinetic energy of 6000 eV. Calculate: (a) the kinetic energy of the electrons in Joules (b) the velocity of the electrons using the formula for the kinetic energy, KE = 1/2 mv^2 and solving for v (c) the cyclotron radius R of their orbits if they travel horizontally "cutting" the vertical magnetic B field of the Earth which at the poles is 0.6 Gauss (d) looking down into the North Pole of the Earth the magnetic field enters the Earth (x). If the electrons come from the East going to the West, which of the two tracks, 1 or 2 in the figure below, will they follow?Explanation / Answer
(A) KE = 6000 eV
= (6000)(1.6 x 10^-19)
= 9.6 x 10^-16 J
(b) 9.6 x 10^16 = (9.109 x 10^-31) v^2 / 2
v = 4.59 x 10^7 m/s
(c) Magntic force = mass x centripetal acc.
q v B = m v^2 / r
r = m v / q B
= (9.11 x 10^-31) (4.59 x 10^7) / (1.6 x 10^-19)(0.6 x 10^-4)
r = 4.36 m
(D) v -> to the right
B -> into the page
q- > negative
F = q ( v X B)
F -> upward
Ans: (1)