- The electric field inside a uniformly charged spherical shell is 0 (Coulomb’s Law), hence \( {(A)-(III)} \).
- The electric field due to a uniformly charged infinite plane sheet is \( \frac{\sigma}{2\epsilon_0} \), hence \( {(B)-(II)} \).
- The electric field outside a uniformly charged spherical shell behaves like that of a point charge and is \( \frac{\sigma}{\epsilon_0 r^2} \), hence \( {(C)-(IV)} \).
- The electric field between two oppositely charged infinite plane sheets is \( \frac{\sigma}{\epsilon_0} \), hence \( {(D)-(I)} \). Thus, the correct answer is \( {(1)} \).

Let $ P_n = \alpha^n + \beta^n $, $ n \in \mathbb{N} $. If $ P_{10} = 123,\ P_9 = 76,\ P_8 = 47 $ and $ P_1 = 1 $, then the quadratic equation having roots $ \alpha $ and $ \frac{1}{\beta} $ is:
An organic compound (X) with molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ is not readily oxidised. On reduction it gives $\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}(\mathrm{Y})\right.$ which reacts with HBr to give a bromide (Z) which is converted to Grignard reagent. This Grignard reagent on reaction with (X) followed by hydrolysis give 2,3-dimethylbutan-2-ol. Compounds (X), (Y) and (Z) respectively are: