Electron Motion in a Long Solenoid

[jehan60188]

Homework Statement

A long solenoid has 100 turns/cm and carries a current i. An electron moves within the solenoid in a circle of radius 0.022 cm perpendicular to the axis of the solenoid. The speed of the electron is 0.048c (c is the speed of light).

Homework Equations

f = m*v^2/r = q*v*B
B of a solenoid = u*n*I
where n = number of turns per meter
u = 4*pi*10^7

The Attempt at a Solution

so B = mv/(r*q) = u*n*I
I = mv/(r*q*u*n)
I = 5436.9 is not correct

 

[BruceW]

your working looks fine to me... But I got a different value for the current when I plugged the numbers in. Maybe that's where the problem is.

 

[jehan60188]

I was using the mass of a proton instead of an electron. replugged the numbers, and it works now!
thanks!