Charging By Induction Using A Negative And Positive Charged Object | BYJU'S

Charging by Induction Using a Positively Charged Object

In this section, 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, sphere A is negatively charged and 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 spheres A and B redistribute, spreading out evenly.

When a positively charged balloon is brought near the sphere system, the electrons from sphere B will migrate towards sphere A due to the force of attraction. Now, sphere A is negatively charged and sphere B is positively charged.

Charging of Electroscope by Induction

An electroscope is an instrument that is used to detect the presence and magnitude of electric charges on a body. An electroscope is commonly used by physics teachers to demonstrate the electrostatic principles of charging and charge interactions.

The demonstration of the induction process of charging is commonly performed with an electroscope. In this demonstration, a charged particle is brought close to but not touching the electroscope. The electrons in the electroscope are induced to move due to the presence of the charged particle above the plate of the electroscope. With the charged particle still held above the plate, the electroscope is touched. At this point, electrons will flow between the electroscope and the ground, giving the electroscope an overall charge. The needle of the electroscope deflects indicating an overall charge when the charged particle is pulled away from it. From this demonstration, the following fundamental principles can be summarised:

• The object being charged by induction never touches the charged particle.
• The charged object does not transfer electrons to or receive electrons from the object being charged.
• The object being charged is touched by the ground; electrons are transferred between the ground and the object being charged (either into the object or out of it).
• The charged object serves to polarize the object being charged.
• The object being charged ultimately receives a charge that is opposite that of the charged object that is used to polarize it.

The application of inductive charging can be divided into high power and low power categories. The low-power applications generally include handheld devices, phones, computers and other devices which charge at power levels below 100 watts. High power inductive charging applications include charging batteries of power levels above 1 kilowatt. The most prominent application is the charging of electric vehicles where automated and wireless inductive charging is provided as an alternative to plug-in charging.

Read More: Electroscope

Review Questions

• List the various differences between electrostatic and electromagnetic induction.

Electromagnetic Induction	Electrostatic Induction
The generation of emf in a conductor due to the rate of change of current in a nearby conductor without any electrical connection.	The accumulation or redistribution of electric charges in a body due to a nearby charged body without any physical contact.
It works for long distances	It works for short distances
It is due to the rate of change of flow of charges	It is due to static charges
The effect is maximum in conductors	The effect is maximum in insulators
Electric fields of the charges are the reason	Magnetic fields due to moving charges are the reason

• Which instrument is used to detect the nature of the charge?

An electroscope is used to detect the nature of the charge.

• How is charging by induction method used in real life?

The charging by induction method is used in charging microphones, smartphones, etc. As induction method is the transfer of charge from one object to another so by placing the phone on the dock charge transfer from dock to phone.

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