Why is the magnetic field felt by a nucleus different in the presence and absencse of electrons? Why is this effect helpful to experimentalists?
Get a scooter to 'drive', you won't have to worry about shifting.
While you need to coordinate clutch and throttle starting out, once you are moving, up shifting is simply a matter of pulling the clutch while reducing throttle, shift, release clutch, go, all very quickly once you get the hang of it.
As I explained yesterday you do not know the basics, if you did you would not be asking how to operate the controls – they are the basics. To learn from a bunch of well-meaning (being charitable) strangers on the internet is going to end in pain and expense. EDIT See, I warned you.
A magnetic field is produced by moving charges. More or less moving charging (ie, those electrons orbiting the nucleus) changes the local magnetic field. It could have any number of helpful effects to scientists, as they can tailor a magnetic field by varying the charge on magnetic materials or electromagnets. Magnetic fields are everywhere, from rail guns to power generators.
