- The electric field within a uniformly charged spherical shell is zero, based on Coulomb's Law, corresponding to \( {(A)-(III)} \).
- The electric field produced by a uniformly charged infinite plane sheet is \( \frac{\sigma}{2\epsilon_0} \), corresponding to \( {(B)-(II)} \).
- Outside a uniformly charged spherical shell, the electric field mimics that of a point charge and is given by \( \frac{\sigma}{\epsilon_0 r^2} \), corresponding to \( {(C)-(IV)} \).
- The electric field situated between two oppositely charged infinite plane sheets is \( \frac{\sigma}{\epsilon_0} \), corresponding to \( {(D)-(I)} \). Therefore, the correct answer is \( {(1)} \).
The center of mass of a thin rectangular plate (fig - x) with sides of length \( a \) and \( b \), whose mass per unit area (\( \sigma \)) varies as \( \sigma = \sigma_0 \frac{x}{ab} \) (where \( \sigma_0 \) is a constant), would be 