Part 1 The aurora is caused when electrons and protons, moving in the earth\'s m
ID: 1396531 • Letter: P
Question
Part 1
The aurora is caused when electrons and protons, moving in the earth's magnetic field of 5.0×105T, collide with molecules of the atmosphere and cause them to glow.
A) What is the radius of the circular orbit for an electron with speed 5.0×106 m/s ?
B) What is the radius of the circular orbit for a proton with speed 3.0×104 m/s ?
Part 2
The unit of current, the ampere, is defined in terms of the force between currents. Two 1.0-meter-long sections of very long wires a distance 2.5 m apart each carry a current of 1.0 A.
What is the force between them? (If the force between two actual wires has this value, the current is defined to be exactly 1 A.)
Explanation / Answer
A) for electron,
Apply, m*v^2/r = q*v*B
r = m*v/(B*q)
= 9.1*10^-31*5*10^6/(5*10^-5*1.6*10^-19)
= 0.57 m
B) for proton,
Apply, m*v^2/r = q*v*B
r = m*v/(B*q)
= 1.6*10^-27*5*10^6/(5*10^-5*1.6*10^-19)
= 1000 m
part 2)
F = mue*I1*I2*L/(2*pi*d)
= 4*pi*10^-7*1*1*1/(2*pi*2.5)
= 8*10^-8 N