Magnetic field on a proton due to an electron

[bennyq]

Homework Statement

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.

Homework Equations

∫B.ds = μI

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?

Homework Statement

Homework Equations

The Attempt at a Solution

 

[rude man]

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

 

[bennyq]

Ahhh i see, yes thankyou