At Saralstudy, we are providing you with the solution of Class 12th physics Electric Charges and Field according to the latest NCERT (CBSE) Book guidelines prepared by expert teachers. Here we are trying to give you a detailed answer to the questions of the entire topic of this chapter so that you can get more marks in your examinations by preparing the answers based on this lesson. We are trying our best to give you detailed answers to all the questions of all the topics of Class 12th physics Electric Charges and Field so that you can prepare for the exam according to your own pace and your speed.

In the first chapter, you will study about the electric charges, fields, and areas in which they are functional. In fact, Physics NCERT Class 12 covers almost all the electric charges types that have been found till now. Also, study the detailed discussion about the transference of electrons along an electric field, electric charges additivity, conservation, quantization, theorems and laws associated with electric charges and electric fields, Gauss; Law, etc. At the end of the lesson answer the questions from the chapter to understand how well you have understood the topic.

Download pdf of NCERT Solutions for Class physics Chapter 1 Electric Charges and Field

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- Q:-
An infinite line charge produces a field of 9 × 10

^{4}N/C at a distance of 2 cm. Calculate the linear charge density. - Q:-
What is the force between two small charged spheres having charges of 2 x 10

^{-7}C and 3 x 10^{-7}C placed 30 cm apart in air? - Q:-
A polythene piece rubbed with wool is found to have a negative charge of 3 × 10

^{−7}C.(a) Estimate the number of electrons transferred (from which to which?)

(b) Is there a transfer of mass from wool to polythene?

- Q:-
A parallel plate capacitor with air between the plates has a capacitance of 8 pF (1pF = 10

^{-12}F). What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6? - Q:-
A 600 pF capacitor is charged by a 200 V supply. It is then disconnected from the supply and is connected to another uncharged 600 pF capacitor. How much electrostatic energy is lost in the process?

- Q:-
A point charge +10 μC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)

- Q:-
A 12 pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor?

- Q:-
A regular hexagon of side 10 cm has a charge 5 µC at each of its vertices. Calculate the potential at the centre of the hexagon.

- Q:-
A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 10

^{3}N/C and points radially inward, what is the net charge on the sphere? - Q:-
Two charges 5 x 10

^{-8}C and -3 x 10^{-8}C are located 16 cm apart. At what point(s) on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero.

- Q:-
**(a)**An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?**(b)**Explain why two field lines never cross each other at any point? - Q:-
Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17.0 × 10

^{−22}C/m^{2}. What is E:(a) in the outer region of the first plate,

(b) in the outer region of the second plate, and

(c) between the plates?

- Q:-
Show that the wavelength of electromagnetic radiation is equal to the de Broglie wavelength of its quantum (photon).

- Q:-
Which among the curves shown in Fig. 1.35 cannot possibly represent electrostatic field lines?

(a)

(b)

(c)

(d)

(e)

- Q:-
A sample of paramagnetic salt contains 2.0 x 10

^{24}atomic dipoles each of dipole moment 1.5 x 10^{-23}J T^{-1}. The sample is placed under a homogeneous magnetic field of 0.64 T, and cooled to a temperature of 4.2 K. The degree of magnetic saturation achieved is equal to 15%. What is the total dipole moment of the sample for a magnetic field of 0.98 T and a temperature of 2.8 K? (Assume Curie's law) - Q:-
Two moving coil meters, M

_{1}and M_{2}have the following particulars:R

_{1}= 10 Ω, N_{1}= 30,A

_{1 }= 3.6 x 10^{-3}m2, B1 = 0.25 TR

_{2}= 14 Ω, N_{2}= 42,A

_{2}= 1.8 x 10-3 m2, B_{2}= 0.50 T(The spring constants are identical for the two meters).

Determine the ratio of (a) current sensitivity and (b) voltage sensitivity of M

_{2}and M_{1}. - Q:-
A circular coil of 20 turns and radius 10 cm is placed in a uniform magnetic field of 0.10 T normal to the plane of the coil. If the current in the coil is 5.0 A, what is the

(a) total torque on the coil,

(b) total force on the coil,

(c) average force on each electron in the coil due to the magnetic field?

(The coil is made of copper wire of cross-sectional area 10

^{-5}m^{2}, and the free electron density in copper is given to be about 10^{29}m^{-3}.) - Q:-
(a) Three resistors 2 Ω, 4 Ω and 5 Ω are combined in parallel. What is the total resistance of the combination?

(b) If the combination is connected to a battery of emf 20 V and negligible internal resistance, determine the current through each resistor, and the total current drawn from the battery.

- Q:-
A point charge causes an electric flux of −1.0 × 10

^{3}Nm^{2}/C to pass through a spherical Gaussian surface of 10.0 cm radius centered on the charge.(a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?

(b) What is the value of the point charge?

- Q:-
In a chamber, a uniform magnetic field of 6.5 G (1 G = 10

^{-4}T) is maintained. An electron is shot into the field with a speed of 4.8 x 10^{6 }m s^{-1}normal to the field. Explain why the path of the electron is a circle. Determine the radius of the circular orbit. (*e*= 1.6 x 10^{-19}C,*m*_{e}= 9.1 x 10^{-31}kg)

- NCERT Chapter

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