How Does Electrostatic Induction Affect Charged Objects?
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 Explained: Concepts & Applications
1. What is electrostatic induction?
Electrostatic induction is a process of temporarily redistributing the electric charges within an object by bringing another charged object near it, without any direct physical contact. When a charged body is brought near a neutral conductor, the free electrons in the conductor move. This results in one side of the conductor developing an excess of charge (becoming negatively charged) and the other side developing a deficiency of charge (becoming positively charged). This separation of charges is known as induced charge.
2. How can a neutral metallic sphere be charged positively using induction?
To charge a neutral metallic sphere positively by induction, follow these steps:
- Step 1: Bring a negatively charged rod near the neutral sphere. The free electrons in the sphere are repelled and accumulate on the side farthest from the rod, leaving the nearer side with a net positive charge.
- Step 2: While the rod is held in place, connect the sphere to the ground (a process called earthing). The repelled electrons from the far side of the sphere will flow into the earth.
- Step 3: Remove the earth connection while the negatively charged rod is still near the sphere. This traps the net positive charge on the sphere.
- Step 4: Finally, remove the charged rod. The excess positive charge will redistribute itself uniformly over the surface of the sphere, making it permanently positively charged.
3. What are some real-world examples and applications of electrostatic induction?
Electrostatic induction has several important real-world applications. A common example is the electrophorus, a device used to generate static electricity. It is also the working principle behind lightning conductors, which safely discharge lightning strikes by guiding the charge to the ground. In technology, electrostatic induction is used in:
- Capacitors: Where charge is stored on plates due to induction.
- Van de Graaff generators: Used in research to produce very high voltages.
- Electrostatic spray painting: Where paint droplets are charged by induction to ensure they evenly coat a grounded object, reducing waste.
4. How can two neutral spheres in contact be charged with equal and opposite charges by induction?
You can charge two conducting spheres with opposite charges using these steps:
- Step 1: Place two uncharged metallic spheres, A and B, on insulating stands, making sure they are in contact with each other.
- Step 2: Bring a positively charged glass rod near sphere A. Due to attraction, free electrons from both spheres will move towards the rod and accumulate on sphere A. This makes sphere A negatively charged. Consequently, sphere B develops a deficiency of electrons and becomes positively charged.
- Step 3: While holding the rod in place, separate the two spheres. This traps the opposite charges on them.
- Step 4: Remove the charged rod. The induced charges will now redistribute uniformly over each sphere. As a result, sphere A will have a net negative charge and sphere B will have a net positive charge.
5. What is the main difference between electrostatic induction and electromagnetic induction?
The primary difference lies in the source of the induction. Electrostatic induction is the redistribution of charge in a conductor due to a nearby static (non-moving) electric field. No current is produced. In contrast, electromagnetic induction is the production of an electromotive force (EMF) or voltage across an electrical conductor in a changing magnetic field. This induced EMF can drive a current, which is the principle behind electric generators and transformers.
6. Why is grounding (or earthing) essential when charging a single conductor by induction?
Grounding is crucial because it acts as a massive reservoir or source of electrons. When charging a single conductor, the initial induction only separates the existing charges. To give the conductor a net charge, you must either remove or add electrons. When a negatively charged rod is brought near a conductor, grounding provides a path for the repelled free electrons to flow away from the conductor into the Earth. Conversely, if a positively charged rod is used, grounding allows electrons to flow from the Earth onto the conductor to neutralize the induced positive charge. Without this connection, the separated charges would simply recombine once the inducing rod is removed, and the conductor would remain neutral.
7. Does the process of charging by induction violate the law of conservation of charge?
No, charging by induction does not violate the law of conservation of charge. This law states that charge can neither be created nor destroyed. In induction, charges are merely redistributed. When a single body is charged by induction with grounding, the charge it gains or loses is balanced by an equal and opposite charge transfer with the Earth. When two bodies are charged by induction, one becomes positive and the other equally negative; the net charge of the two-body system remains zero. The inducing body itself does not lose any of its charge in the process.
8. Why does electrostatic induction occur effectively in conductors but not in insulators?
This difference is due to the availability of mobile charge carriers. Conductors, like metals, have a large number of free electrons that are not bound to individual atoms and can move freely throughout the material. When an external charge is brought near, these free electrons can easily move, leading to a significant separation of charge. Insulators, on the other hand, have electrons that are tightly bound to their atoms and cannot move freely. While a slight charge separation can occur through a phenomenon called dielectric polarization (where the electron clouds of atoms distort slightly), it is a much weaker effect and does not result in the large-scale charge redistribution seen in conductors.
