List of top Physics Questions on Electrostatics and Potential Energy

Two short dipoles \( (A, B) \), \( A \) having charges \( \pm 2\,\mu\text{C} \) and length \( 1\,\text{cm} \) and \( B \) having charges \( \pm 4\,\mu\text{C} \) and length \( 1\,\text{cm} \) are placed with their centres \( 80\,\text{cm} \) apart as shown in the figure. The electric field at a point \( P \), equidistant from the centres of both dipoles is \underline{\hspace{2cm}} N/C.

Two charges $7 \mu C$ and $-2 \mu C$ are placed at $(-9, 0, 0)$ cm and $(9, 0, 0)$ cm respectively in an external field $E = \frac{A}{r^2}\hat{r}$, where $A = 9 \times 10^5 \text{ N/Cm}^2$. Considering the potential at infinity is 0, the electrostatic energy of the configuration is ___ J.
A point charge of \(10^{-8}\) C is placed at origin. The work done in moving a point charge 2 \(\mu\)C from point A(4, 4, 2) m to B(2, 2, 1) m is_______ J. (\(\frac{1}{4\pi\epsilon_0} = 9 \times 10^9\) in SI units)
If an alpha particle with energy 7.7 MeV is bombarded on a thin gold foil, the closest distance from nucleus it can reach is_____ m.
(Atomic number of gold = 79 and \(\frac{1}{4\pi\epsilon_0}=9\times10^{9}\) SI units)
A parallel plate capacitor has capacitance C, when there is vacuum within the parallel plates. A sheet having thickness \( \frac{1}{3}d \) of the separation between the plates and relative permittivity K is introduced between the plates. The new capacitance of the system is:

For a short dipole placed at origin O, the dipole moment P is along the X-axis, as shown in the figure. If the electric potential and electric field at A are V and E respectively, then the correct combination of the electric potential and electric field, respectively, at point B on the Y-axis is given by:

For a short dipole placed at origin O
Two point charges \( q \) and \( 9q \) are placed at a distance of \( l \) from each other. Then the electric field is zero at a
Two charges \( 7 \, \mu C \) and \( -4 \, \mu C \) are placed at \( (-7 \, \text{cm}, 0, 0) \) and \( (7 \, \text{cm}, 0, 0) \) respectively. Given, \( \epsilon_0 = 8.85 \times 10^{-12} \, \text{C}^2 \text{N}^{-1} \text{m}^{-2} \), the electrostatic potential energy of the charge configuration is: