Charging by Conduction

General

Charging by conduction, or also known as charging by contact, is the transfer of electrons from a charged object to a neutral object that requires a physical connection. There can be two cases of charging by conduction, that is to either use a negatively charged object or a positively charged object.

Charging by Conduction – Negatively Charged Object

When a neutral object meets a negatively charged object, it will become negatively charged as well. To make sense of this, we must understand that a negatively charged object has an excess amount of electrons. Electrons need their own space, and so repel from one another. The electrons in a neutral object is not packed together, so when a neutral object comes in contact with a negatively charged object, a bridge is formed and allows the excess of electrons to run towards the open space. When the electrons move, the negatively charged object stays negative, and the neutral object gains more electrons, hence charging it negatively.

Charging by Conduction – Positively Charged Object

In a positively charged object, the number of protons is excessive. Unlike electrons, protons are attached to the neutrons, thus cannot move around as easily. When a positively charged object comes in contact with a neutral object, it will attract the electrons. To understand why the electrons would leave its comfortable conditions in the neutral object, we must know that electrons and protons’ purpose is to help balance the ones in need. When the positively charged object rubs off the neutral one, the electrons in the neutral one notice the excessive amount of protons and move to it. The positively charged object stays positive with less excessive protons, and the amount of electrons in the neutral object reduces, ergo it becomes a positively charged object.

Resource: http://www.physicsclassroom.com/class/estatics/u8l2c.cfm

For an animation, click below:
Conduction - Negative and Positive