What do you call the process of charging a conductor by bringing it near another object?

In this section, we shall learn about the transfer of charge by induction using a negatively charged object. Let us consider two metal spheres A and B touching each other, as shown in the figure. Let us take a negatively charged rubber balloon. If we bring the charged balloon near the spheres, electrons within the two-sphere system will be induced to move away from the balloon due to the repulsion between the electrons of the balloon and the spheres. Subsequently, the electrons from sphere A get transferred to sphere B.The migration of electrons causes sphere A to become positively charged and sphere B to be negatively charged. The overall two-sphere system is hence electrically neutral. The spheres are then separated using an insulating cover such as gloves or a stand as shown in the figure (avoiding direct contact with the metal). When we remove the balloon, the charge gets redistributed, spreading throughout the spheres, as shown in the figure.

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.

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

• List the various differences between electrostatic and electromagnetic induction.

• 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.

To learn more about charging by induction and other related topics, download BYJU’S – The Learning App.

The process of supplying the electric charge (electrons) to an object or losing the electric charge (electrons) from an object is called charging. An uncharged object can be charged in different ways.

When an object is rubbed over another object, the electrons get transferred from one object to another. This transfer of electrons takes place due to friction between the two objects. The object that transfers electrons loses negative charge (electrons) and the object that accepts electrons gains negative charge (electrons).

Hence, the object that gains extra electrons becomes negatively charged and the object that loses electrons becomes positively charged. Thus, the two objects get charged by friction. The charge obtained on the two objects is called friction charge. This method of charging an object is called electrification by friction.

The process of charging the uncharged object by bringing it in contact with another charged object is called charging by conduction.

A charged object has unequal number of negative (electrons) and positive charges (protons). Hence, when a charged object is brought in contact with the uncharged conductor, the electrons get transferred from charged object to the conductor.

Consider an uncharged metal rod A kept on an insulating stand and a negatively charged conductor B as shown in below figure (1). 

If we touch the uncharged conductor A with the negatively charged conductor B, transfer of electrons from charged conductor to uncharged conductor takes place. Hence, uncharged conductor gains extra electrons and charged conductor loses electrons. Thus, uncharged conductor A becomes negatively charged by gaining of extra electrons.

Similarly, uncharged conductor becomes positively charged if it is brought in contact with positively charged conductor.

The process of charging the uncharged object by bringing another charged object near to it, but not touching it, is called charging by induction.

Consider an uncharged metal sphere and negatively charged plastic rod as shown in below figure (1). If we bring the negatively charged plastic rod near to uncharged sphere as shown in below fig (2), charge separation occurs.

The positive charges in the sphere get attracted towards the plastic rod and move to one end of the sphere that is closer to the plastic rod. Similarly, negative charges get repelled from the plastic rod and move to another end of the sphere that is farther away from the plastic rod. Thus, the charges in the sphere rearrange themselves in a way that all the positive charges are nearer to the plastic rod and all the negative charges are farther away from it.

If this sphere is connected to a ground through the wire as shown in fig (3), free electrons of the sphere at farther end flow to the ground. Thus, the sphere becomes positively charged by induction. If the plastic rod is removed as shown in fig (4) all the positive charges spread uniformly in the sphere.