The neutron is a particle with zero charge still it has a non-zero magnetic moment with z-component `9.66 xx 10^(-27) A-m^(2)`. This can be explained by the internal structure of the neutron. The evidence indicates that a neutron is composed of three fundamental particles calleed quarks : an `"up"` (u) quark, of charge `+ (2e)/(3)`, and two `"down"` (d) quarks, each of change `- (e)/(3)`. The combinations of the three quarks prodcues a net charge of `(2e)/(3) - e/3 - e/3 = 0`.

If the quarks are in motion they can produce a non-zero magnetic moment. As a very simple model, suppose the u quark moves in a counter clockwise circular path and the d quarks move in a clockwise circular path, all of the radius r and all with the same speed v see figure.
The current due to the circular motion of the u quark :-

Options

A. `(ev)/(6pir)`
B. `(ev)/(3pir)`
C. `(ev)/(pir)`
D. `(2ev)/(pir)`

Answer

B

Explanation

`i=qf=((2e)/3)(v/(2pir))=(ev)/(3pir)`