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Electrostatic Induction

Last updated date: 24th Feb 2024
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Define Electrostatic Induction

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

  • Bringing plastic rod near a conducting metal plate

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.

  • Bringing charged object near an electroscope

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. 

FAQs on Electrostatic Induction

1. How charging by induction can be done using a negatively charged object?

Let us take two metal objects A and B that are touching each other. Take a negatively charged rubber balloon. Now, bring the charged balloon near the objects, electrons in the two metal objects will be induced to move away from the balloon due to the repulsion between the electrons of the balloon and the metal objects.  Now, the electrons will get transferred from object A to object B. the transferring of electrons causes object A to become positively charged and object B will become negatively charged. But, the overall system of two objects is neutral. Now, the objects can be separated using an insulating cover. When we remove the balloon, the charge will get distributed, spreading throughout the metal objects.

2. How charging by induction can be done using a positively charged object?

Take two metal spheres A and B that touch each other. Now, bring a positively charged balloon near sphere A. The electrons from sphere B will get transferred from sphere B to sphere A due to attractions between the opposite charges. This will reduce the number of electrons in sphere B. The sphere A will become negatively charged and the sphere B will become positively charged. Now, separate the two spheres using an insulating cover. When the balloon is removed, the charge will get redistributed in spheres A and B thus spreading evenly. 

3. How can we charge a neutral sphere by induction process?

Consider a neutral sphere made with metal positioned on an insulator sheet. Then a negatively charged rod is brought closer to the sphere. The sphere is neutral implies that it has both positive as well as negative charges. Bringing the negatively charged rod closer causes repulsion of the negative charges in the sphere. As a result, these negative charges will move to the outer side of the sphere. If grounded, then these negative charges will move to the ground. Thus, only positive charges will remain and spread on the sphere after removing the rod. In this way, the neutral sphere attains a positive charge by the process of electromagnetic induction. 

4. What is the application of charging by induction process in real life?

An object can attain electrical charges by not coming in contact with another charged object. In real life, one can observe the process of electrostatic induction in commercial products governed with induction coils. The smartphones and the charging dock consist of induction coils of iron covered with copper wire. When a phone is placed on the charging dock, it produces an electromagnetic field between the induction coils. After the production of the electromagnetic field, electricity passes between induction coils. As a result, the phone charges wirelessly. In this way, a phone can be charged without even actual contact, but bringing it closer to the charging dock.

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