The electrical resonance in Square shaped planar THz Split Ring Resonators (Sq- SRR) is observed at all polarizations of the incident wave. This resonance has been conventionally attributed to dipole oscillations in the arms parallel to the incident E -field (vertical arm), while neglecting the effect of arm perpendicular to the incident E -field (horizontal arm) that has been described in the past as the cut-wire approximation. In order to study the effect of horizontal arm on electrical resonance, several geometrical modifications of SqSRR consisting of identical vertical arms with varying horizontal arm lengths, were designed, fabricated and characterized at frequencies from 0.1 to 0.3 THz, at normal incidence. Contrary to the cut wire approximation, significant shift in electrical resonance frequency was observed with varying horizontal arm lengths of SqSRR. The presented experimental results and analysis based on the surface current profile in these structures, indicate the necessity to include the effect of horizontal arm in design of SqSRR. The shifts in plasma frequency with variation in horizontal arm length is explained as dilution of the effective electron density of the vertical arm. Simple modification in existing models for plasma frequency and electrical resonance frequency is proposed to consider the effect of horizontal arm lengths. Experimental and simulated results were found to be in good agreement with the proposed model.