If n denotes a positive integer, h the Planck's constant, q the charge and B the magnetic field, then the quantity nh2πqB has the dimension of  [WB JEE 2014]

The quantity is given as nh2πqB, where n and 2π  are 2 π are dimensionless quantities.∵  mvr=nh2π                                         …(i)Also using, Bqr = mv⇒              Bq = mv/r                               …(ii)Using Eqs. (i) and (ii), we get            nh2πqB=mr˙rmv/r=r2As, r has the dimension of length, thus the given quantity has the dimension of area.