Science (English Medium) इयत्ता १२ - CBSE Important Questions for Physics

Why should electrostatic field be zero inside a conductor?

Why must electrostatic field be normal to the surface at every point of a charged conductor?

Why is electrostatic potential constant throughout the volume of the conductor and has the same value (as inside) on its surface?

A capacitor of 200 pF is charged by a 300 V battery. The battery is then disconnected and the charge capacitor is connected to another uncharged capacitor of 100 pF. Calculate the difference between the final energy stored in the combined system and the initial energy stored in the single capacitor.

Why is there no work done in moving a charge from one point to another on an equipotential surface?

A hollow metal sphere of radius 10 cm is charged such that the potential on its surface is 5 V. What is the potential at the centre of the sphere?

Net capacitance of three identical capacitors in series is 2 μF. What will be their net capacitance if connected in parallel?

Find the ratio of energy stored in the two configurations if they are both connected to the same source.

A parallel plate capacitor is being charged by a time varying current. Explain briefly how Ampere’s circuital law is generalized to incorporate the effect due to the displacement current ?

Depict the equipotential surfaces for a system of two identical positive point charges placed a distance(d) apart?

Deduce the expression for the potential energy of a system of two point charges q₁ and q₂ brought from infinity to the points `vecr_1`and `vecr_2`respectively in the presence of external electric field `vecE`.

A parallel-plate capacitor is charged to a potential difference V by a dc source. The capacitor is then disconnected from the source. If the distance between the plates is doubled, state with reason how the following change:

(i) electric field between the plates

(ii) capacitance, and

(iii) energy stored in the capacitor

Can two equi-potential surfaces intersect each other? Give reasons.

Two charges −q and +q are located at points A (0, 0, −a) and B (0, 0, +a) respectively. How much work is done in moving a test charge from point P (7, 0, 0) to Q (−3, 0, 0)?

Three identical capacitors C₁, C₂ and C₃ of capacitance 6 μF each are connected to a 12 V battery as shown.

Find

(i) charge on each capacitor

(ii) equivalent capacitance of the network

(iii) energy stored in the network of capacitors

The figure show a network of five capacitors connected to a 10V battery. Calculate the charge acquired by the 5μF capacitor.

An ac circuit consists of a series combination of circuit elements X and Y. The current is ahead of the voltage  in phase by `pi /4` . If element X is a pure resistor of 100Ω ,

(a)  name the circuit element Y.
(b)  calculate the rms value of current, if rms value of voltage is  141V.
(c)  what will happen if the ac source is replaced by a dc source ?

Derive an expression for the electric potential at any point along the axial line of an electric dipole.

Draw the equipotential surfaces due to an electric dipole.

The figure shows a network of five capacitors connected to a 100 V supply. Calculate the total energy stored in the network.