The influence of magnetic field on the homogeneously aligned nematic liquid crystal materials with positive dielectric anisotropy to exhibit williams domains as threshold effect is theoretically investigated. These investigations indicate three types of positive dielectric nematics known as weakly positive, moderately positive and strongly positive. The plot of stabilization term for domain formation with dielectric anisotropy clearly indicates the three regions. Frequency dependence of threshold voltage at different values of magnetic field and dielectric anisotropies has been calculated which agrees with the earlier results. The effects of dielectric anisotropy on the existence of domain formation in the positive Delta is an element of nematitics and the variation of threshold voltage with Ae are numerically calculated and compared with experimental results.