An electron is orbiting is a circular orbit of radius r under the influence of a constant magnetic field of strength B. Assuming that Bohr postulate regarding the quantisation of angular momentum holds good for this elerctron, find
(a) the allowed values of te radius r of the orbit.
(b) the kinetic energy of the electron in orbit
(c ) the potential energy of insteraction between the magnetic moment of the orbital current due to the electron moving in its orbit and the magnetic field B.
(d) the total energy of the allowed energy levels.
(e) the total magnetic flux due to the magnetic field B passing through the nth orbit. (Assume that the charge on the electronis -e and the mass of the electron is m).

Answer

B, C, D

Explanation

(a) `r = (mv)/(Be) ….(i)`
`mvr = (nh)/(2pi) ….(ii)`
Solving these two equations, we get
`r = sqrt((nh)/(2piBe))`
and` v = sqrt((nhBe)/(2pim^2))`
(b) `K = (1)/(2) mv^2 = (nhBe)/(4pim)`
(c ) `M = iA =((e )/(T)) (pir^2)`
`=(e )/((2pir)/(v)) (pir^2) = (evr)/(2)``
`=` (e )/(2) sqrt((nh)/(2piBe)) sqrt((nhBe)/(2pim^2)`
`=(nhe)/(4pim)`
`U =- MB cos 180^@`
`=(nhe)/(4pim).`