NCERT Solutions for Class 12 Physics Chapter 2

Radius of the spherical conductor, r = 12 cm = 0.12 m Charge is uniformly distributed over the conductor, q = 1.6 × 10⁻⁷ C Electric field inside a spherical conductor is zero. This is because if there is field inside the conductor, then charges will move to neutralize it.

Capacitances of the given capacitors: C₁ = 2 pF, C₂ = 3 pF and C₃ = 4 pF For the parallel combination of the capacitors, equivalent capacitor is given by Ceq the algebraic sum, Therefore Ceq = C₁ + C₂ + C₃ = 2 + 3 + 4 = 9 pF Therefore, total capacitance of the combination is 9 pF.

Dielectric constant of the mica sheet, k = 6 If voltage supply remained connected, voltage between two plates will be constant. Supply voltage, V = 100 V Initial capacitance, C = 1.771 × 10⁻¹¹ F New capacitance, C₁ = kC = 6 × 1.771 × 10⁻¹¹ F = 10⁶ pF New charge, q₁ = C₁V = 10⁶ × 100 pC = 1.06 × 10⁻⁸ C Potential across the plates remains 100 V.

Yes The electric field intensity inside a cavity is zero, even if the shell is not spherical and has any irregular shape. Take a closed loop such that a part of it is inside the cavity along a field line while the rest is inside the conductor. Net work done by the field in carrying a test charge over a closed loop is zero because the field inside the conductor is zero. Hence, electric field is zero, whatever is the shape.

When a charged particle is moved from one point to the other on a closed loop, the work done by the electrostatic field is zero. Hence, the tangential component of electrostatic field is continuous from one side of a charged surface to the other.

The force between two conducting spheres is not exactly given by the expression, Q₁ Q₂/4πϵ₀r², because there is a non-uniform charge distribution on the spheres.

Gauss’s law will not be true, if Coulomb’s law involved 1/r³ dependence, instead of1/r², on r.

Yes, If a small test charge is released at rest at a point in an electrostatic field configuration, then it will travel along the field lines passing through the point, only if the field lines are straight. This is because the field lines give the direction of acceleration and not of velocity.

Whenever the electron completes an orbit, either circular or elliptical, the work done by the field of a nucleus is zero.

No Electric field is discontinuous across the surface of a charged conductor. However, electric potential is continuous.

The capacitance of a single conductor is considered as a parallel plate capacitor with one of its two plates at infinity.

Water has an unsymmetrical space as compared to mica. Since it has a permanent dipole moment, it has a greater dielectric constant than mica.

We do not get an electric shock as we step out of our house because the original equipotential surfaces of open air changes, keeping our body and the ground at the same potential.

Yes, the man will get an electric shock if he touches the metal slab next morning. The steady discharging current in the atmosphere charges up the aluminium sheet. As a result, its voltage rises gradually. The raise in the voltage depends on the capacitance of the capacitor formed by the aluminium slab and the ground.

The occurrence of thunderstorms and lightning charges the atmosphere continuously. Hence, even with the presence of discharging current of 1800 A, the atmosphere is not discharged completely. The two opposing currents are in equilibrium and the atmosphere remains electrically neutral.

During lightning and thunderstorm, light energy, heat energy, and sound energy are dissipated in the atmosphere.