Binding Energy

The concept of Binding energy is an abstract one and many people find it confusing. Binding energy is important to understanding the structure of matter and is an idea we will use often in this course.

Definition of Binding energy - the amount of energy required to increase an object's potential energy to zero.

This definition implies that is possible and acceptable for object to have negative potential energy. How is this so?

Example 1

When we consider the gravitational potential energy (GPE) of objects we usually designate a horizontal axis where GPE = 0. For example if a football were lying on the ground or a book on a tabletop we would say that the GPE of the football or book is zero. If we dug a hole and placed the football in it, or placed the book on the ground we would then decrease the GPE of the football and book to a negative value (according to our reference frame). The binding energy in these cases would be the energy required to get the football out of the hole or put the book on the table.

Example 2

Suppose we sprinkle iron fillings on a magnet. Say the potential energy of the iron is zero when it is not in contact with the magnet. This would imply that the iron filling has a negative potential energy when it is stuck to the magnet. To remove the iron from the magnet we need energy, and this energy is called the binding energy.

List other possible examples of negative potential energies and binding energies .