•Can derive                    N = number of plates

•

•    N = 16 (tR/Wb)2                Wb = base width

•

•    N = 16 (tR/4s)2   = (tR/s)2

•

•    N = 5.54 (tR/W½)2                 W½ = width at  

•                                                     half height

•Column manufacturers use N

•to characterize column – N varies widely