Electrostatics means it is the branch of physics which deals study of charge at rest.
- Charge (q): –Charge is an intrinsic property of matter due to which it experiences Electrostatic forces of attraction and repulsion.
There are two types of Charges
- Properties of Electric Charge
Attraction and repulsion: Like charges is known as Loving charges repel each other | Unlike charges is known as Hating charges attract each other.
- Additive properties of charge: Charge is additive in nature i.e. total charge on a body is the algebraic sum of all charges present on the body.
- Quantisation of charge: It is defined as the integral multiple of Fundamental charge on a single electron.
- Charge of electron 1.6 x 10-19C is known as fundamental charge on single electron.
Where e is the charge of electron and n = 1, 2, 3,…
- Principle of conservation of charge: “Charge can neither be created nor be destroyed it can be transferred from one system to another.”
-Total charge in an isolated system is constant.
- Method of charging:
– Charging by rubbing: When insulating materials rub against each other, they may become electrically charged. Electrons, which are negatively charged, may be ‘rubbed off’ one material and on to the other. The material that gains electrons becomes negatively charged. The material that loses electrons is left with a positive charge.
Eg- When a polythene rod is rubbed with a duster, the friction causes electrons to gain energy. Electrons gain enough energy to leave the atom and ‘rub off’ onto the polythene rod.
–
Conduction (Charging by touching method):
Charging by conduction involves the contact of a charged object to a neutral object. Hence when an uncharged conductor is brought in contact with a charged conductor, charge is shared between the two conductors and hence the uncharged conductor gets charged. During charging by conduction, both objects acquire the same type of charg
–Induction (Charging by contact): The induction charging is a charging method that charges an object without actually touching the object to any another charged object. The charging by induction process is where the charged particle is held near an uncharged conductive material that is grounded on a neutrally charged material. The charge flows between two objects and the uncharged conductive material develop a charge with opposite polarity.
- Charging by induction using a negatively charged object:
We shall learn about the transfer of charge by induction using a negatively charged object. Let us consider two metal spheres A and B touching each other, as shown in the figure. Let us take a negatively charged rubber balloon. If we bring the charged balloon near the spheres, electrons within the two-sphere system will be induced to move away from the balloon due to the repulsion between the electrons of the balloon and the spheres. Subsequently, the electrons from sphere A get transferred to sphere B.The migration of electrons causes the sphere A to become positively charged and the sphere B to be negatively charged. The overall two-sphere system is hence electrically neutral. The spheres are then separated using an insulating cover such as gloves or a stand as shown in the figure (avoiding direct contact with the metal). When we remove the balloon, the charge gets redistributed, spreading throughout the spheres, as shown in the figure.
- Charging by induction using a positively charged object:
We shall learn about the transfer of charge through the process of induction using a positively charged object. Taking two spheres A and B, touching each other, as shown in the figure, if we bring a positively charged balloon near sphere A, the electrons from sphere B migrate towards sphere A due to the attraction between opposite charges, thus leaving the sphere B deficit of electrons. As a result, the sphere A is negatively charged and the sphere B is positively charged. The spheres are then separated using an insulating cover, a stand or gloves. When the balloon is removed, the charges in sphere A and B redistribute, spreading out evenly.
- Coulomb’s law
The magnitude of electrostatic force between two point objects is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them and acts along the line joining their centres.
- Coulomb’s law in vector form
- When charge placed in a medium
- Electric Field
-A region around a charged particle or object within which a force would be exerted on other charged particles or objects.
-Symbol of electric field denoted ‘E’.
-S.I unit of electric field N/C
-Formula
- Electric field due to point charge
Physics Class 12th Very Very Important Questions With Solutions..
Class 12th Physics Very Important Questions With Answers ||
50+ Physics Very Important Questions With Answer||
Physics Class 12th MCQs| for Class 12th Chapter Wise Answers| Sample Paper 2021-22
Physics Class 12th Important Questions With Solutions | Electric Charge and Field | {CBSE-NIOS}
Physics Class 12th Important Questions With Solutions | Electric Charge and Field | {CBSE-NIOS}
