Charging by Conduction

             Charging by conduction is done when a charged object comes in contact with a neutral one, and a transfer of electrons occur between the two. Upon receiving the electrons from the charged object, there will be a change in the charge of the neutral object.            

A charged object consists of only one type of charge, either a negative one or a positive one. If an object consists of both, it is considered neutral. Upon understanding that like charges repel and have the need to spread further away from each other, you should know that the farthest that they are able to travel to, is only within the space of the object. You should also know that the electrons in a charged object are more tightly packed than those in a neutral object. So if a path to a neutral object becomes available, these electrons will cross it in order to find more free space. By moving from the charged space to the neutral one, the electrons have affected the neutral state of charge, therefore causing the neutral object to become charged as well.

               

Charging by Conduction Using a Negatively Charged Object

When conduction charging is done by a negatively charged object, the charged object consists of excess electrons. When  the charged object comes in contact with the neutral object, these excess electrons will travel to the neutral space, causing the neutral object to also become negatively charged.

Charging by Conduction Using a Positively Charged Object

When conduction charging is done by a positively charges object, the same process occurs, except there is an excess number of protons instead of electrons. These excess protons, when in contact with a neutral object, will be transferred to the neutral space, causing it to become positively charged.

Resources: http://www.studyphysics.ca/30/charging.pdf

                  http://www.physicsclassroom.com/Class/estatics/u8l2c.cfm