Important Questions for Class 12 Chapter 1 - Electric Charges and Fields

Important questions based on NCERT syllabus for Chapter 1 - Electric Charges and Fields:

Question-1: Whenever we rub a glass rod with a silk cloth, then a charge appears on both. We can observe this similar phenomenon on a lot of other pair of materials. Explain this phenomenon. How can we relate this observation with the law of conservation of charge?

Solution: When we rub two bodies together then a charge is developed on both of the bodies and the charge developed over the bodies are equal but opposite in nature. And this phenomenon of getting a charge is called as charge by friction. The net charge on both of the bodies is 0 and the reason behind it is that an equal amount of charge is also repelling it. When we rubbed the glass rod with the silk cloth, there will be charge with opposite magnitude is generated over there. This phenomenon is in consistence with the law of conservation of energy. A similar phenomenon is observed with many other pairs of bodies.

Question-2: (i) ‘electric charge of a body is quantised’, explain the statement.
(ii) While dealing with macroscopic i.e., large scale charges we can ignore quantisation of charge. Why?

Solution: (i) Electric charge of a body is quantized meaning only integral (1, 2, …n) number of electrons can be transferred from a body to another.
Charges do not get transferred infractions. Hence, the total charge possessed by a body is only in integral multiples of electric charge.
(ii) In the case of large scale or macroscopic charges, the charge which are used over there are comparatively too huge to the magnitude of the electric charge. Hence, on a macroscopic level the quantization of charge is of no use Therefore, it is ignored and the electric charge is considered to be continuous.

Question-3: (i) Explain why an electric field cannot have a sudden break? Explain why “An electrostatic field is a continuous curve”
(ii) Can two field line cross each other? Explain why?

Solution: (i) When a charge is placed in an electrostatic field then it experiences a continuous force. Therefore, an electrostatic field line is a continuous curve. And a charge moves continuously and does not jump from on point to the other. So, the field line cannot have a sudden break.

(ii) if two field lines will cross each other at any point then at that point the field intensity will start shooing two directions at a same point which is impossible. Therefore, two field lines can never cross each other.