[Physics Class Notes] on Electrostatic Induction Pdf for Exam

The process of generating or producing electricity in a material by bringing an electrically charged object near it refers to electrostatic induction. It causes the charges to get redistributed in that material. As a result, one side of the material has an excess of positive charges, and another side has negative charges. Many students get confused when they have to define electrostatic induction for conducting and non-conducting materials. The article below helps study the process of induction in electrostatics, along with some examples.

How can One Charge a Material through Induction?

Electrostatic induction is the physical phenomenon in which a material can be charged without any actual contact with a charged body. On bringing two substances close to each other, due to the induction property, some movement of charge carriers from one object to another. 

The above picture shows how a metal sphere attains positive charges on bringing a charged rod close to it.

Electrostatic Charging by Induction in a Conducting Material

The phenomenon of electrostatic charging by induction is most efficient when objects are conducting materials like metals. A conducting material often has an equivalent number of positive and negative charges in the neutral state. On bringing an electrically charged object near this conductor, the object’s charges start attracting the opposite charges and repelling the like charges. 

Example of Electrostatic Induction

The plastic rod’s negative charges start attracting the positive charges of the metal plate when it is brought near it. Additionally, the negative charges repel the negative charges within the metal plate. It creates a relocation of electrical charges within the metallic plate. The electrical charges will remain in the redistributed state as long as the charged rod is kept near the plate. However, with the removal of the electrically charged rod, the metal plate loses its charge instantaneously. It is because of the thermal motion of the atoms that causes the charges to integrate again.

An electroscope is an example of electrostatic induction. On bringing the charged object like the plastic rod near an electroscope, opposite charges start moving towards an electroscope’s metallic end. As a result, the metal shaft’s electrical charges get redistributed, and negative charges gather at the other end. It is vital to note here that the electroscope has not gained any electrical charge. Charges are only redistributed with positive charges on the top and negative charges at the end of the electroscope. On removing the charged rod, charges produced in the electroscope intermix again, and the endpoints come back to a neutral state. However, a conductor can hold charges with the induction phenomenon if grounded. 

Some of the Principles Illustrated in the above Examples of Charge Induction

When the object is not grounded, then an electrically charged object will induce equal and opposite charges in that object.

An electrically charged object does not receive or transfer any electrons to the object going to get induced.

When the inducing object is near, and any part of the material is grounded, then a charge opposite in polarity will get attracted. On the contrary, the object will consist of the charge that is opposite to the inducing charge.

Electrostatic Charging by Induction in a Non-Conducting Material

The process of induction in electrostatics is also beneficial in giving electric charge to certain non-conducting materials. It is produced by the polarization of molecules of non-conducting materials. However, the movement of charges is quite controlled in non-conductors as compared to conducting materials. The free movement of electrons in a conductor enables the flow of electricity in a metal. Unlike conductors, the electrons are inhibited within the atoms in non-conductors. Due to this reason, the separation of charged particles does not work in the case of non-conducting materials. Polar molecules have one side consisting of more positive ions compared to the other side. If the non-conductor consists of these molecules, then induction of electrostatics causes alignment of positive charges on one side and negative charges on the opposite side of the molecule. An example of a water molecule can explain electrostatic induction in non-conducting materials. The H₂O molecule has positive charges on one side and negative charges on another side. Hence, it is possible to observe the induction of charge in a water stream when a charged plastic comb is close to it.

By bringing an electrically charged object near to a neutral material, charges can be produced in that material. It is an effective process of creating static electricity, especially with conducting materials. Temporarily grounding the conductor does not allow the immediate loss of charges produced on removing the charged object.

Applications of Electromagnetic Induction

Some applications of electromagnetic induction are given here:

• Electrostatic induction means redistribution of electrical charges in an object produced due to the influence of nearby charges.  The most common application of electromagnetic induction is in the Vande Graph generator and Wimshurst machine.

• In an electric generator the coils are rotated in the static magnetic field due to which the magnetic field will change. There is a change in the reflux due to which electromotive force is produced. 

• The second application of electromagnetic induction is graphic tablets. 

• Next, it is also used in induction cooling.