We have examined how the magnitude of the polar cap potential for northward interplanetary magnetic field (IMF) changes with the angle of the field in the BX/BZ plane. From the dawn-dusk passes (November--December 1981, May--June 1992, and November--December 1982) of the Dynamics Explorer 2 satellite, we selected 363 passes by requiring the IMF hourly value BZ≥1 nT for the preceding 2-hour interval. Of these, 72 cases displayed a reverse convection pattern in the electric field data, i.e., sunward at the highest latitudes and antisunward at lower latitudes. The potential difference across the region of sunward convection correlates well with various functions that consist of all or some of the IMF parameters, BZ, BY, the BY/BZ angle, and the solar wind velocity. We ''normalize'' the potential, using these functions. To test for a BX dependence while eliminating dipole tilt effects, we introduce ϕh *, the angle between the IMF vector projected to the X-Z meridian and the earth dipole axis. The normalized potential F for the northern hemisphere is the largest when ϕh *, measured from the northern dipole axis toward the Sun, is negative and large (~-100¿), and decreases as ϕh * approaches zero and turns positive. An approximate equation for this relations is F(ϕh *)=a+b/(ϕh *+125¿), where the values for a and b lie between 0.0086 and 0.015 and between 1.6 and 1.9, respectively. This relation can be interpreted in terms of a model of magnetosheath field line motion which predicts that the reconnection belt on the magnetopause poleward of the cusp becomes longer as the magnetosheath field lines tilt toward the tail lobe. ¿ American Geophysical Union 1995.