Did you know? Brushing your shoes makes it easier for them to get dust, in other words, they attract dust. This is all because of electrostatic forces. Let’s dig in and find out more.
LEARNING OBJECTIVES
By the end of this topic, you are expected to,
Electrostatics refers to a branch of physics responsible for the study of electric charges at rest. From the time of classical physics, materials like amber have been known to attract particles of lightweight after rubbing. Electrostatic phenomena come from the forces that electric charges exert on one another. These forces can be described by Coulomb’s law. Even though electrostatically induced forces seem to be weak, some electrostatic forces like the one between a proton and an electron, that together produce a hydrogen atom, is approximately 36 orders of magnitude stronger than the gravitational force that acts between them.
Examples of electrostatic phenomena are very many. Some are very simple, like the attraction of a plastic wrap to the hand after removing from a package. Others are more spontaneous, like the explosion of grain silos, photocopier and laser printer operation, and damage of electronic components during manufacturing. Electrostatics is all about the buildup of charges on the surface of objects as a result of contact with other surfaces. Although the exchange of charges happens whenever any two surfaces come into contact and separate, the effects of the exchange of charges are normally only noticed when at least one of the surfaces has a high resistance to the flow of electricity. The reason is that the charges that transfer are trapped there for enough time that their effects can be observed. These charges then remain on the object until they are quickly neutralized by a discharge or bleed off to the ground. For example, the popular phenomenon of a static shock is a result of the neutralization of charge built up in the body from the contact with surfaces that are insulated.
COULOMB’S LAW
This law states that: “the magnitude of the electrostatic force of repulsion or attraction between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them”.
The force is along the straight line that joins them. In cases where the two charges have the same sign, the electrostatic force between them is repulsive; in cases where they have different signs, the force between them is attractive.
ELECTRIC FIELD
The electric field in units of newtons per coulomb or volts per meter refers to a vector field that can be defined everywhere, apart from at the location of point charges (this is the point where it diverges into infinity). It is defined as the electrostatic force in newtons on a small test charge at the point due to Coulomb’s law, divided by the magnitude of the charge in coulombs.
Electric field lines are important and are used for visualizing the electric field. These lines start on a positive charge and end on a negative charge. They are also parallel to the electric field’s direction at each point, and the density of these field lines is a measure of the magnitude of the electric field at any given point.
