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Charging by Induction is defined as the charges of an object without allowing it to come into contact with another charged object. Charged particles are kept near an uncharged conductive substance grounded on a neutrally charged surface using the charging by induction method.
Read Also: Class 12 Electric Charges and Fields
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Keywords: Charging by Induction, Charges, Negatively Charged Object, Positively Charged Object, Electroscope Induction Charging, Electrons
Charging by Induction with a Negatively Charged Object
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Consider A and B, two metal spheres that are in contact, as illustrated below. Take a rubber balloon that's been negatively charged. To induce electrons in the two-sphere system to migrate away from the charged balloon, bring it close to them.
This causes electrons to repel one another, which causes them to move away from the balloon. The electrons in sphere A are then transported to sphere B. Electron migration makes sphere A positive charge and sphere B negative charge.
As a result, the total two-sphere system is electrically neutral. To separate the spheres, use gloves or a stand (like the one in the illustration) (avoiding direct contact with the metal). When the balloon is removed, the charge is redistributed and can be seen spreading among the spheres in the illustration.
Because of repulsion, when an electrically negative balloon is brought close to a positively charged system, the electrons in the system move away from the balloon and away from the sphere.
Sphere A becomes positive due to the migration of electrons, while sphere B becomes negatively charged.
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Charging by Induction with a Positively Charged Object
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A positively charged balloon is held near two concentric spheres A and B as depicted in the illustration. This causes electrons from sphere B to migrate to the positively charged balloon, depleting sphere B's supply of electrons.
As a result, sphere A is negatively charged while sphere B is positively charged. An insulating cover, a stand, or gloves are then used to separate the spheres. When the balloon is popped, the charges in spheres A and B redistribute themselves evenly.
Due to the force of attraction, electrons from sphere B will migrate towards sphere A when a positively charged balloon is brought close to the sphere system.
Now, sphere A has a negative charge, while sphere B has a positive charge.
Read Further: Maxwell’s Equation
Electroscope Induction Charging
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An electroscope is a device that detects the presence and quantity of electric charges on a body. Physics teachers frequently utilize an electroscope to show the electrostatic principles of charging and charge interactions.
An electroscope is widely used to demonstrate charging by induction. In this demonstration, a charged particle is brought close to the electroscope, but not touching it. The charged particle above the electroscope's plate induces the electrons to move, and this causes the electrons to move.
The electroscope is contacted while the charged particle is still being held above the plate. At this point, electrons will pass between the electroscope and the ground, charging the electroscope in total.
Electroscope's needle deflects when a charged particle is moved away from it, indicating an overall charge.
Key ideas based on this demonstration:
- The charged particle is never touched by the thing being charged through induction.
- The charged object does not exchange electrons with or receive electrons from the charged object.
- A ground comes into contact with the charged object, and electrons are exchanged between the ground and the charged object, either into or out of it.
- The charged object is used to polarise the charged object.
- The charged object eventually obtains a charge that is the polar opposite of the charged object that was used to polarise it.
Uses of Induction Charging
Induction charging has two main uses: high- and low-power. Handheld gadgets, cell phones, computers, and other electronic devices that use less than 100 watts of power are considered low-power applications.
Applications for high-power inductive charging include charging batteries with a power rating of more than 1 kilowatt. As an alternative to traditional plug-in charging, inductive charging is most commonly used to charge electric automobiles.
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Previous Year Questions
- An electric dipole of moment…. [KEAM]
- An electron enters uniform electric field maintained by parallel plates and of….[KEAM]
- Electric lines of force about a positive point charge are….[KEAM]
- Charge is a…… [KEAM]
- One kilowatt hour is equal to….[NEET 1997]
- The resistance of a wire is ′R′ ′ ohm. If it is melted and stretched to ′n′ times its original length, its new resistance will be :…..[NEET 2017]
- If the ammeter has a coil of resistance 480ohm and a shunt of 20ohm , the reading in the ammeter will be….[NEET 2015]
- If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be….[NEET 2003]
- The internal resistance of the battery is...[NEEt 2011]
Things to Remember
- Using induction charging saves time and energy, which makes it the preferred charging technique for many different gadgets.
- In commercial items, induction coils regulate the charging process.
- Iron induction coils wrapped in the copper wire are found in the charging dock as well as the phone itself in smartphones. An electromagnetic field is generated between the induction coils when the phone is docked.
- After the electromagnetic field has been created, electricity can move between the two induction coils and charge the phone wirelessly.
Check Important Notes for Surface Charge Density Formula
Sample Questions
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Ques. What does it mean to charge using induction technology? (1 Mark)
Ans. Induction charging is a charging method that does not require the object to be in contact with any other charged objects.
Ques. Is it true that stroking anything leaves it charged? (1 Mark)
Ans. Rubbing does not charge all items.
Because rubbing is a process by which one body transfers its charge to another, both bodies must have what is known as an electrostatic property known as Charge at rest when rubbing together.
Ques. What's the purpose of an electroscope? (1 Mark)
Ans. In an electroscope, a pair of thin gold leaves dangling from an electrical conductor leading to the outside of an insulating container is used to detect the presence of an electric charge or ionizing radiation.
Ques. What is the best way to generate a positive charge? (1 Mark)
Ans. Transferring electrons to or from an object generates an electrical charge. Negatively charged objects are created by the addition of negatively charged electrons to a positively charged system. A thing becomes positively charged once electrons have been taken from it.
Ques. When two uncharged objects come into contact, what happens? (1 Mark)
Ans. Electrons can be knocked loose and caught up by the other object when two neutral things come into touch, especially in a dry atmosphere. When an object receives electrons, it becomes negatively charged, and when an object loses electrons, it becomes positively charged.
Ques. By convention, the charge on a glass rod that has been rubbed with silk is (3 Marks)
1.) Positive
2.) Negative
3.) Either positive or negative
4.) None of the above
Ans. Due to rubbing a glass rod with a silk cloth,
- The glass rod has free electrons that are lost and given to the silk cloth
- Thus, the glass rod loses electrons and hence becomes positively charged
- The silk cloth is now having extra electrons hence gains a negative charge
So, the correct option is - the glass rod when rubbed with a silk cloth becomes POSITIVE or POSITIVELY CHARGED.
Ques. A positively charged iron rod is brought close without touching a neutral sphere of aluminum. The aluminum sphere is grounded with wire, when the wire is removed the aluminum sphere will become: (4 Marks)
1.) Positive
2.) Negative
3.) Remain uncharged
4.) Can't say
Ans. If a charged body is brought near an uncharged body, then one side of the neutral body (closer to charged body) becomes oppositely charged while the other side becomes similarly charged.
- In charging by induction the charged body does not touch the uncharged body.
- In charging by induction the charge generated on the uncharged body will be opposite as the charge on the charged body.
EXPLANATION:
- When we bring a positively charged iron rod near a sphere of aluminum, the electrons in the sphere will move towards the rod and accumulate on the rod side due to attraction.
- After that, if the sphere is grounded with a wire then the electrons from the earth will start moving towards the sphere.
- After that, if the wire is removed then the sphere will become negatively charged. Hence, option 2 is correct.
Ques. Which of the following is/are the charging method? (5 Marks)
1.) Charging by friction
2.) Charging by conduction
3.) Charging by induction
4.) All of the above are charging methods.
Ans. CONCEPT:
- Electric charge is a conserved quantity, which means Electric charge can be neither created nor destroyed.
- Methods of Charging: The process of supplying the electric charge to an object or losing the electric charge from an object is called charging.
- There are mainly three charging methods:
- Charging by friction ( triboelectric charging)
- Charging by conduction
- Charging by induction
- Charging by Conduction: The method of charging an uncharged object by bringing it close to a charged object is known as charging by conduction.
- The charged conductor has an unequal number of protons and electrons, hence when an uncharged conductor is brought near it, it discharges electrons to stabilize itself.
- Charging by Friction: When two objects are rubbed against each other, charge transfer takes place.
- One of the objects gains electrons while the other object loses electrons.
- The object that gains electrons becomes negatively charged and the object that loses electrons becomes positively charged.
- Charging by Induction: The process of charging an uncharged conductor by bringing it near a charged conductor without any physical contact is known as charging by induction.
EXPLANATION:
The main charging methods are:
- Charging by friction ( triboelectric charging)
- Charging by conduction
- Charging by induction
- Charging by contact
So all the options are correct.
Hence the correct answer is option 4.
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