电磁感应定律(双语)

When the induced electromotive force is generated in the coil, there is an electric field to push the charges to move in the coil, and this induced electric field is denoted as E.
The law of electromagnetic induction is one of basic laws for time-varying electromagnetic fields, and it is also one of Maxwell’s equations.
2. Inductances
1. Law of Electromagnetic Induction
From physics we know that when the magnetic flux through a
closed coil is changing, an induced electromotive force e will be
Considering SB dS , we have
lE
dl
t
SB
dS
eI
Which is called the law of electromagnetic induction, and it shows that when the magnetic field through a closed coil is changing, an induced electric field will be generated in the coil.
If the magnetic flux is increased with time, the direction of the induced electromotive force and that of the magnetic flux obey the left hand rule. if the magnetic flux is decreased with time, they will obey the right hand rule.
In a linear medium, the magnetic flux through the closed circuit is also proportional to the current I.
The magnetic flux linked with the current I is called the magnetic
eI
The induced magnetic flux caused by the induced current in the coil always resists the change of the original magnetic flux. The induced magnetic flux is called the reaction magnetic flux, and the induced electromotive force is called the back electromotive force.
generated in the coil, with the relation
e
d dt
eI
where the positive direction of the electromotive force e and that of the magnetic flux comply with the left hand rule.
The line integral of the induced electric field intensity around
the closed coil is equal to the induced electromotive force in the coil
e, i.e.
lE
dl
e
d dt
flux linkage with the current I, and it is denoted as . The ratio of
The law of electromagnetic induction shows that a time-varying magnetic field can produce a time-variable electric field.
Based on Stokes’ theorem, from the above equation we have
Chapter 6 Electromagnetic Induction
Law of Electromagnetic Induction Inductances
Energy and Force
1. Law of Electromagnetic Induction 2. Inductances 3. Energy in Steady Magnetic Fields 4. Magnetic Forces
S
(
E)
B t
dS
0
Since the equation holds for any area S, the integrand must be zero, so
that
E
B tcalled the differential form of law of electromagnetic induction, and it means that the negative time rate of change of the magnetic flux density at a point is equal to the curl of the timevariable electric field intensity at that point.