13. A particle of mass m and charge q is circling on an orbit of radius R normal to an external magnetic field Bext. This moving charge would create a new magnetic field. What is this new magnetic field at the center of the orbit?
(A)
(B)
(C)
(D)
(E) None of the above.
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統計: A(1), B(0), C(0), D(0), E(0) #3858169
統計: A(1), B(0), C(0), D(0), E(0) #3858169