List of top Physics Questions on Electrostatics asked in CBSE Class Twelve Board Exam

Two infinitely long straight wires ‘1’ and ‘2’ are placed \(d\) distance apart, parallel to each other, as shown in the figure. They are uniformly charged having charge densities \(\lambda\) and \(-\frac{\lambda}{2}\) respectively. Locate the position of the point from wire ‘1’ at which the net electric field is zero and identify the region in which it lies.

A charge \( -6 \mu C \) is placed at the center B of a semicircle of radius 5 cm, as shown in the figure. An equal and opposite charge is placed at point D at a distance of 10 cm from B. A charge \( +5 \mu C \) is moved from point ‘C’ to point ‘A’ along the circumference. Calculate the work done on the charge.

A metal sheet is inserted between the plates of a parallel plate capacitor of capacitance C. If the sheet partly occupies the space between the plates, the capacitance:

Two point charges \( 5 \, \mu C \) and \( -1 \, \mu C \) are placed at points \( (-3 \, \text{cm}, 0, 0) \) and \( (3 \, \text{cm}, 0, 0) \), respectively. An external electric field \( \vec{E} = \frac{A}{r^2} \hat{r} \) where \( A = 3 \times 10^5 \, \text{V m} \) is switched on in the region. Calculate the change in electrostatic energy of the system due to the electric field.

The electric field at a point in a region is given by \( \vec{E} = \alpha \frac{\hat{r}}{r^3} \), where \( \alpha \) is a constant and \( r \) is the distance of the point from the origin. The magnitude of potential of the point is:

In the figure, curved lines represent equipotential surfaces. A charge \( Q \) is moved along different paths A, B, C, and D. The work done on the charge will be maximum along the path:

A charge \( Q \) is distributed over two concentric hollow spheres of radii \( r \) and \( R \) (\( R>r \)) such that their surface charge densities are equal. Find: \begin{enumerate} \item the electric field, and \item the potential at their common center. \end{enumerate}

A charge \( -6 \, \mu C \) is placed at the center B of a semicircle of radius 5 cm, as shown in the figure. An equal and opposite charge is placed at point D at a distance of 10 cm from B. A charge \( +5 \, \mu C \) is moved from point C to point A along the circumference. Calculate the work done on the charge.

Figure shows variation of Coulomb force (F) acting between two point charges with \( \frac{1}{r^2} \), \( r \) being the separation between the two charges \( (q_1, q_2) \) and \( (q_2, q_3) \). If \( q_2 \) is positive and least in magnitude, then the magnitudes of \( q_1, q_2 \), and \( q_3 \) are such that:

In the circuit shown, the charge on the left plate of the 20 µF capacitor is \( -50\,\mu C \). The charge on the right plate of the 12 µF capacitor is:

Two small solid metal balls A and B of radii \(R\) and \(2R\) having charge densities 2 and 3 respectively are kept far apart. Find the charge densities on A and B after they are connected by a conducting wire.

A charge \( Q \) is fixed in position. Another charge \( q \) is brought near charge \( Q \) and released from rest. Which of the following graphs is the correct representation of the acceleration of the charge \( q \) as a function of its distance \( r \) from charge \( Q \)?

Read the following paragraphs and answer the questions that follow.
A parallel plate capacitor consists of two conducting plates kept generally parallel to each other at a distance. When the capacitor is charged, the charge resides on the inner surfaces of the plates and an electric field is set up between them. Thus, electrostatic energy is stored in the capacitor.
The figure shows three large square metallic plates, each of side ‘L’, held parallel and equidistant from each other. The space between P1 and P2, and P2 and P3 is completely filled with mica sheets of dielectric constant ‘K’.
The plate P2 is connected to point A and the other plates P1 and P3 are connected to point B. Point A is maintained at a positive potential with respect to point B and the potential difference between A and B is V .

Two point charges Q and \( -q \) are held \( r \) distance apart in free space. A uniform electric field \( \vec{E} \) is applied in the region perpendicular to the line joining the two charges. Which one of the following angles will the direction of the net force acting on charge \( -q \) make with the line joining Q and \( -q \)?

A body acquires charge \( 8.0 \times 10^{-12} \, \text{C} \). The mass of the body:

Two point charges of \( -5\,\mu C \) and \( 2\,\mu C \) are located in free space at \( (-4\,\text{cm}, 0) \) and \( (6\,\text{cm}, 0) \) respectively.
(a) Calculate the amount of work done to separate the two charges at infinite distance.
(b) If this system of charges was initially kept in an electric field \[ \vec{E} = \frac{A}{r^2}, \text{ where } A = 8 \times 10^4\, \text{N}\,\text{C}^{-1}\,\text{m}^2, \] calculate the electrostatic potential energy of the system.

A circuit consisting of a capacitor \( C \), a resistor of resistance \( R \), and an ideal battery of emf \( V \), as shown in the figure, is known as an RC series circuit.

As soon as the circuit is completed by closing key \( S_1 \) (keeping \( S_2 \) open), charges begin to flow between the capacitor plates and the battery terminals. The charge on the capacitor increases and consequently the potential difference \( V_C = \frac{q}{C} \) across the capacitor also increases with time. When this potential difference equals the potential difference across the battery, the capacitor is fully charged (\( Q = VC \)). During this process of charging, the charge \( q \) on the capacitor changes with time as: \[ q = Q\left( 1 - e^{-\frac{t}{RC}} \right) \] The charging current can be obtained by differentiating it and using: \[ I = \frac{dq}{dt} = \frac{V}{R} e^{-\frac{t}{RC}} \] Consider the case when \( R = 20 \, \text{k}\Omega \), \( C = 500 \, \mu\text{F} \), and \( V = 10 \, \text{V} \).

The final charge on the capacitor, when key \( S_1 \) is closed and \( S_2 \) is open, is: