Magnetic fields can induce current in conductors. The strength of the current is determined by multiple factors, which will be discussed theoretically with the appropriate formulas shown in this lesson.
To understand electromagnetic induction, we must introduce a few theoretical concepts. The most important one that you are probably seeing for the first time is electromagnetic flux. The electromagnetic flux is directly proportional to the surface area of a circuit and to the magnetic field acting on it. Since the strength of the magnetic field describes how many field lines pass through a unit of area, we can see that flux is used to describe how many total field lines pass through an area. The formula for the electromagnetic flux reads as follows:
\[\Phi = B \times A\]
Where:
Because of this, another name for the strength of the magnetic field is also called the magnetic flux density, because it describes how dense the magnetic field lines are in an observed area. The unit for electromagnetic flux is Wb.
Physicist Maxwell proved that there exists a correlation between the magnetic and electric fields. The change in a magnetic field induces an electric field, and a change in the electric field induces a magnetic field.
Because a change in the magnetic field results in an induction of an electric field, the magnetic field can indirectly induce a current using the induced electric field.
Maxwell also proved that the lines of an induced electric field are closed; they don’t have a start nor a finish.
To be more precise, an electromotive force is needed for a current to exist, so the magnetic field induces the electromotive force, which creates the current. The electromotive force induced by the magnetic field is only dependent on the component of the field that is perpendicular to the surface of the circuit. So, if the angle between the magnetic field and the circuit is \(\theta\), then the perpendicular component of the field with strength B would be equal to \(B \times \sin \theta\)
Written by Nemanja Maslak