15. A particle of mass m and charge q is in a circular orbit (of radius R) normal to anexternal fiel
問題詳情
15. A particle of mass m and charge q is in a circular orbit (of radius R) normal to anexternal field B.What is proportional to the magnetic field created at the center of itsorbit by the charge? (A) m； (B) q； (C) R； (D) B； (E) None.