参考书：
初级：
Purcell, E. M., Electricity and Magnetism Berkeley Physics Course, Vol. 2.
Probably the best of the introductory-level texts; elegantly written and carefully illustrated.
中级
Griffiths, D. J., Introduction to Electrodynamics.
The standard undergraduate text at the intermediate level, with clear explanations and informal style.
Lorrain, P., Corson, D., and Lorrain, F., Electromagnetic Fields and Waves.
Another excellent intermediate-level text, with detailed explanations supported by helpful diagrams.
Wangsness, R. K., Electromagnetic Fields.
Also a great intermediate-level text, --> Jackson.
高级
Jackson, J. D., Classical Electrodynamics.
The standard graduate text, but you must be solidly prepared before embarking.
其他：
Cottingham W. N. and Greenwood D. A., Electricity and Magnetism.
A concise survey of a wide range of topics in electricity and magnetism.
Schey, H. M., Div, Grad, Curl, and All That. Norton, New York, 1997.
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Why do physicists and engineers always talk about small test charges? Because the job of
this charge is to test the electric field at a location, not to add another electric field into the
mix (although you can’t stop it from doing so). Making the test charge infinitesimally
small minimizes the effect of the test charge’s own field.
=
Φ：flux
Φᴇ： flux of field E
electric flux Φᴇ = number of field lines penetrating surface
ε0：The electric permittivity of free space
The permittivity of a material determines
its response to an applied electric field – in nonconducting materials
(called ‘‘insulators’’ or ‘‘dielectrics’’), charges do not move freely, but
may be slightly displaced from their equilibrium positions.
the permittivity of a medium is a fundamental parameter in determining the
speed with which an electromagnetic wave propagates through that
medium.
P37
The key factor in determining the divergence at any
point is not simply the spacing of the field lines at that point, but whether
the flux out of an infinitesimally small volume around the point is greater
than, equal to, or less than the flux into that volume.
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CH2
The key difference in the electric field and magnetic field versions of
Gauss’s law arises because opposite electric charges (called ‘‘positive’’
and ‘‘negative’’) may be isolated from one another, while opposite
magnetic poles (called ‘‘north’’ and ‘‘south’’) always occur in pairs.
To date, all efforts to detect magnetic monopoles have failed, and every magnetic north pole is
accompanied by a magnetic south pole.这实验是怎么做的？在磁铁里面放探针么？
the net magnetic flux passing through any closed surface must be zero
because magnetic field lines always form complete loops.
Faraday’s law：
Thus, the circulation of the induced electric field is the energy given to
each coulomb of charge as it moves around the circuit.
E ：The induced electric field
But charge-based electric fields have field lines that originate on positive charge and terminate on
negative charge (and thus have non-zero divergence at those points),
while induced electric fields produced by changing magnetic fields have field lines that loop back on themselves, with no points of origination or termination (and thus have zero divergence).
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The Ampere–Maxwell law
μ0：magnetic permeability of free space
Maxwell and his contemporaries did realize that Ampere’s law as ori-
ginally conceived applies only to steady electric currents, since it is con-
sistent with the principle of conservation of charge only under static
conditions. To better understand the relationship between magnetic fields
and electric currents, Maxwell worked out an elaborate conceptual model
in which magnetic fields were represented by mechanical vortices and
electric currents by the motion of small particles pushed along by the
whirling vortices(NB的数学建模，哪里能看到他是如何建模的？). When he added elasticity to his model and allowed
the magnetic vortices to deform under stress, Maxwell came to understand
the need for an additional term in his mechanical version of Ampere’s law.
Most texts use one of three approaches to demonstrating the need for the changing-flux term in the Ampere–Maxwell law:
- conservation of charge,
- special relativity,
- an inconsistency in Ampere’s law when applied to a charging capacitor.
displacement current：
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5 From Maxwell’s Equations to the wave equation
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αβγδεζηθικλμνξοπρςστυφχψω
ΓΔΘΛΞΠΣΦ
ᴱᴇ
