Question:
A charged particle of charge e and mass m is moving in an electric field E and magnetic field B. Construct dimensionless quantities and quantities of dimension [T]-1.
Solution:
mv2/R = evB
eB/m = v/R = ꞷ
B = F/ev = [MA-1T-2] [ꞷ] = [eB/m]=[v/R] = [T-1]