Why is flux important?

What does it mean by change of magnetic flux?

• I have a formula ; Voltage = Change in Magnetic flux / Change in time So what does it mean by change of magnetic flux? How can I calculate the change in magnetic flux? This is how you calculate the magnetic flux = Tesla(Magnetic feild) X Surface area (cm^2) So by that formula, I have the magnetic flux, but how can I calculate the change in magnetic flux? and change in time?

• Answer:

  We often visualize magnetic fields as lines forming loops that begin and end on a magnet. The amount of magnetic flux is proportional to the number of lines, measured in units called Webers (Wb). The strength of a magnetic field is measured not by just the total number of lines, but by their density, which is proportional to the number of lines that passes perpendicularly through a unit area, measured in units of Webers per square meter (Wb/m^2), or Tesla (T). Note: A traditional unit of magnetic flux was actually called a "line" . It has been replaced by the Weber in the SI system of units. Faraday's Law of Induction says that if the amount of flux passing through a wire loop varies then an electrical voltage will be induced in the loop. The amount of flux can change if the strength of the field changes, or if the size of the loop changes, or if the loop moves. The law is just as you have stated above: Voltage = Change in Magnetic flux / Change in time Written more compactly it is: V = ΔF / Δt where Δ means a change in a quantity, F for flux and t for time. The above formula is true if the flux changes smoothly over a given time interval. For example, if you move the magnet away from the wire loop smoothly over a period of 2 s, and as a result the enclosed flux decreases from 5 Wb to 2 Wb, the induced voltage will be: V = (5 Wb - 2 Wb)/2 s = 3/2 = 1.5 Volts If you use calculus, the law applies to sudden changes too: V = dΦ/dt where Φ is the usual symbol for magnetic flux.