Flux vs Flux Density
Flux and flux density are two very important concepts discussed in the theory of electromagnetics. Flux is the amount of the field through a particular surface. Flux density is the amount of the field going through a unit area. Both of these ideas are very important in fields such as electromagnetics, power and electrical engineering, physics and many more fields. A thorough understanding in these concepts is required in order to excel in such fields. In this article, we are going to discuss what flux and flux density are, their definitions, the applications of flux and flux density, the similarities of flux and flux density, and finally the difference between flux and flux density.
Flux is a conceptual property. In fields such as electric, magnetic, electromagnetic and gravitational field, a term called flux is defined in order to describe the field. To understand what flux is one must first understand the concept of lines of force. For an example, magnetic field lines or magnetic lines of forces are a set of imaginary lines which are drawn from N (north) pole of the magnet to the S (south) pole of the magnet. In definition these lines never cross each other unless the magnetic field intensity is zero. It must be noted that magnetic lines of forces are a concept. They don’t exist in real life. It is a model which is convenient to compare magnetic fields qualitatively. For electric fields, the lines are drawn from the positive end to the negative end. The flux over a surface is said to be proportional to the number of lines of forces perpendicular to the given surface. The flux is denoted by the Greek letter ψ. The concept of flux holds a very special place in the electromagnetic induction. In electromagnetic induction, the current flowing through a closed conducting loop is proportional to the rate change of magnetic flux over the closed surface which is created by the conducting loop.
The flux is not enough to understand the true nature of a given field. The best way to describe a field is the flux density. Flux density gives the amount of the field passing through a unit area for the given surface. Flux density is also known as field intensity. Even though the term flux is a conceptual term the flux density has a numerical value, and units. The flux density at a point is proportional to the strength of the field at that particular point.
What is the difference between Flux and Flux Density?
• The term flux has no units whereas flux density is a quantity with units.
• Flux cannot be measured, but flux density can be measured.
• The flux does not give a clear idea about the nature of the field, but the flux density gives a very good model for the field.
• Flux density can be identified as the amount of the field going normal through a given unit surface.