| Static_Electricity Website by Jeremy Smallwood on static electricity. Describes the physics phenomena, possible electrostatic damages, materials for electrostatic solutions, and standards. Gives advice on solution of co |
| Static_Electricity_Projects Site devoted to projects utilizing static electricity (motors, generators) which are simple enough and can be relatively easily built. |
| Vacuum_Tube_Diode A demonstration of how a vacuum tube diode works. |
| The_Van_de_Graaff_Generator_Website This site includes information on how Van de Graaff Generators work, typical classroom demonstrations, and instructions for building one. |
| VRML_Gallery_of_Electromagnetism Visualization of the electromagnetic field. |
| Wireless_Lab_at_Nizhny_Novgorod_University Laboratory of Physical Fundamentals and Technologies of Wireless networks at Nizhny Novgorod State University, Russia. |
| Wondermagnet_com Images of magnets and their uses, experiments, a discussion board about magnet-related topics, and an elementary primer on magnetism and magnetic physics. |
| X-ray_Optics_and_Microscopy_at_Stony_Brook Research describing use of coherent soft X-rays for optics experiments, including Fresnel zone plates, to produce the smallest focused spot of electromagnetic waves for studies of biological and mater |
| NSSDC__Venus From NASA's photo gallery. |
| Planet_Venus_-_overview_and_pictures Illustrated guide to Venus. Contains description, facts, statistics and a brief history. |
| Venus From The Nine Planets. |
| Venus NASA's Windows to the Universe. |
| Venus Details on this planet. |
| Venus From "Views of the Solar System". |
| Venus Facts, early knowledge and history of man's exploration of Venus. |
| Venus_Basic_Information Summary articles and related links. |
| Venus__Earth\'s_troubled_sister Although it looks a lot like Earth, it's actually dramatically different. |
| Welcome_to_the_Planets__Venus Planetary profile and vital statistics, some pictures. |
| ACalendar_com The calendar has many options with a standard monthly interface, including sunrise, sunset, and Moon phases. |
| Annus_Novus_Decimal_Calendar A proposal for a non-sectarian, culturally neutral calendar system. |
| Astro_Portal_-_CalSKY The worldwide interactive online astronomical/space calendar and calculator - for friends of astronomy, as well as astronomers. |
| Astronomical_Time_Keeping Extensive descriptions of many astronomical time keeping systems, with information on time zones and Julian day numbers. |
| Astronomy_by_JavaScript__Sun_Calculators_and_More Applets related to calendars and keeping time, including sidererial time. |
| Astronomy_Calendar Features different views of the night sky, constellations, stars, planets, and other celestial wonders. |
| Blue_Moon_Myths Second full moon in a month, or third full moon in a single season? |
| Britannica_com_-_Clockworks__From_Sundials_to_the_Atomic_Second Britannica.com explores the history of timekeeping, from sundials to cesium atomic clocks. |
| The_Calendar,_Leap_Years_and_the_Year_2000 An explanation of the calendar including the origin of the day, week, month and year. |
| Calendar_Studies Articles on the Gregorian and Julian calendars, the ISO date format, the Julian day number system, the Maya calendar, the Goddess lunar calendar, the Liberalia Triday Calendar and C functions for date |
| Calendars_through_the_Ages History and FAQs of calendars, from ancient Rome to outer space. Including Julian, Gregorian, Jewish, Islamic, Chinese, and Mayan. |
| Calendopaedia The Encyclopaedia of Calendars. |
| Calendrical_Calculations Published by Cambridge University Press. Gives a unified algorithmic presentation of the Gregorian, ISO, Julian, Coptic, Ethiopic, and Islamic civil calendars. |
| The_Chinese_Calendar The mathematics of the Chinese calendar. Explains the rules for the Chinese calendar. |
| The_Difference_Between_the_Millennium_and_Year_2000 Questions and answers to satisfy the hearts of true millennium buffs. |
| Greenwich_Time__Home_of_World_Time_(GMT)_since_1884 Complete guide to times in every time zone in the world. |
| Hindu_Calendar_Dates_52nd_Century Explains the cosmological and astronomical influences in creating the Indian calendar. |
| Indian_Moons A list of many American Indian tribe's names for months, days, and other calendar related information. |
| The_Islamic_Calendar The mathematics of the Islamic calendar in Singapore. |
| The_Julian_and_Gregorian_Calendars Explanations of the Julian Calendar, the Gregorian Reform, the adoption of the Gregorian Calendar, the length of the tropical year and related matters. |
| Julian_Day_Numbers An explanation of the Julian day number system used by astronomers and calendricists. |
| Leap_Seconds Civil time is occasionally adjusted by one second increments called leap seconds. A detailed explanation of what a second actually is, and why leap seconds are necessary. |
Next: Mean Free PathUp: No Title Previous: Mandelstam Variables 
(Other system units are discussed e.g. in [Jackson75].) 
is the electric field, 
is the displacement, 
the permittivity of free space and 
the polarization. 
is the magnetic induction (magnetic flux density), 
the magnetic field, 
the permeability of free space and 
the magnetization. 
is the density of electric charge and 
is the current density. The relations between 
, and between 
, are called constitutive equations; they describe the medium. In a linear, isotropic medium 
and 
, where 
and 
are constants. In general 
where c is the speed of light in vacuum and by definition 
The continuity equation 
follows from Maxwell's equations and expresses the conservation of electric charge.Defining the scalar potential 
and vector potential 
by 
explicitly solves half of Maxwell's equations. The potentials are not unique, since any gauge transformation 
leaves the physical fields 
being an arbitrary function.Other types of potentials may be useful in certain cases (e.g. a scalar potential for 