An electric dipole placed in an electric field of intensity $2 \times {10}^5 \mathrm{N}/\mathrm{C}$ at an angle of $30°$ experiences a torque equal to $4 \mathrm{Nm}$. The charge on the dipole of dipole length $2 \mathrm{cm}$ is

Why is the conductivity of a n-type semiconductor greater than that of p-type semiconductor even when both of these have same-level of doping?

A uniformly charged solid sphere of radius R has potential $V_0$ (measured with respect to $\infty$ ) on its surface. For this sphere the equipotential surfaces with potential $\frac{3V_0}{2},\frac{5V_0}{4},\frac{3V_0}{4}$ and $\frac{V_0}{4}$ have radius $R_1$ , $R_2, R_3$ and $R_4$ respectively. Then

Note : This question had two option correct at the time of examination. Proper corrections are made in the question to avoid it.