




For a uniformly charged thin spherical shell of radius \( R \) and total charge \( Q \), the electric potential inside the shell (\( r < R \)) is constant and equal to the potential at the surface:
\( V = \frac{kQ}{R} \)
where \( k \) is Coulomb's constant. This means the potential does *not* change as you move from the center towards the surface.
For points outside the shell (\( r > R \)), the electric potential is the same as that of a point charge located at the center of the shell:
\( V = \frac{kQ}{r} \)
The potential decreases as the distance \( r \) increases, following an inverse relationship.
Based on the above analysis:
This corresponds to a graph that is constant for \( r < R \) and then decreases hyperbolically for \( r > R \).
The correct graphical representation is Option (4).
Two charges, \( q_1 = +3 \, \mu C \) and \( q_2 = -4 \, \mu C \), are placed 20 cm apart. Calculate the force between the charges.
You are given a dipole of charge \( +q \) and \( -q \) separated by a distance \( 2l \). A sphere 'A' of radius \( R \) passes through the centre of the dipole as shown below and another sphere 'B' of radius \( 2R \) passes through the charge \( +q \). Then the electric flux through the sphere A is
A substance 'X' (1.5 g) dissolved in 150 g of a solvent 'Y' (molar mass = 300 g mol$^{-1}$) led to an elevation of the boiling point by 0.5 K. The relative lowering in the vapour pressure of the solvent 'Y' is $____________ \(\times 10^{-2}\). (nearest integer)
[Given : $K_{b}$ of the solvent = 5.0 K kg mol$^{-1}$]
Assume the solution to be dilute and no association or dissociation of X takes place in solution.
Inductance of a coil with \(10^4\) turns is \(10\,\text{mH}\) and it is connected to a DC source of \(10\,\text{V}\) with internal resistance \(10\,\Omega\). The energy density in the inductor when the current reaches \( \left(\frac{1}{e}\right) \) of its maximum value is \[ \alpha \pi \times \frac{1}{e^2}\ \text{J m}^{-3}. \] The value of \( \alpha \) is _________.
\[ (\mu_0 = 4\pi \times 10^{-7}\ \text{TmA}^{-1}) \]