Homework Help: Magnetic field on a proton due to an electron

1. Aug 24, 2014

bennyq

1. The problem statement, all variables and given/known data
In Niels Bohr's 1913 model of the hydrogen atom, an electron circles the proton at a distance of 5.29 E-11 m with a speed of 2.19E6 m/s. Compute the magnitude of the magnetic field this motion produces at the location of the proton.

2. Relevant equations
∫B.ds = μI

3. The attempt at a solution
I found the time it takes the electron to circle the proton,
then the current(I)
by dividing the Q(electron)/time

then i take ds to be 2∏r and B to be constant for the integral..

I got 3.99T, the solution gets 12.5T and uses 2r for the vector ds around the path.
Not sure how the path can be 2r?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Aug 24, 2014

rude man

Ampere's law doesn't seem appropriate. Consider Biot-Savart instead.

3. Aug 24, 2014

bennyq

Ahhh i see, yes thankyou