A small sphere with mass `1.2 g` hangs by a thread between two parallel vertical plates `5.00 cm` apart. The plates are insulating and have uniform surface charge densities `+ sigma and - sigma`. The charge on the sphere is `q = 9 xx 10^-6 C`. What potential difference between the plates will cause the thread to assume an angle of `37^(@)` with the vertical as shown in (Fig. 3.134) ?
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