Classical electromagnetism

Classical electromagnetism is a theory of physics that describes the interaction of electric and magnetic fields at macroscopic scales. It was developed in the late 19th century by physicists such as James Clerk Maxwell and Michael Faraday. Classical electromagnetism precedes quantum physics.

  • Classical electromagnetism is based on the idea that electric charges and electromagnetic fields are continuous and smooth. It does not take into account the quantization of energy or the wave-particle duality of matter.
  • Charged particles create electromagnetic fields, which in turn exert electromagnetic forces on other charged particles.
  • The four Maxwell equations are:
    • Gauss’s law for electricity: The electric flux through a closed surface is proportional to the total electric charge enclosed by the surface.
    • Gauss’s law for magnetism: There are no magnetic monopoles, and the magnetic flux through a closed surface is always zero.
    • Faraday’s law of induction: A changing magnetic field produces an electric field.
    • Ampere’s circuital law with Maxwell’s correction: A changing electric field or an electric current produces a magnetic field.
  • These equations can be used to describe a wide range of phenomena, from the propagation of electromagnetic waves to the operation of electrical and electronic devices. They are also used in many different fields, including engineering, medicine, and astronomy.
Core concepts of classical electromagnetism
  • Charged Particles (Matter): These are particles that have an electric charge, either positive (protons) or negative (electrons). They are the sources of electric and magnetic fields and are affected by these fields.
  • Electromagnetic Force: This force is a fundamental interaction between charged particles. It can be attractive or repulsive, depending on the sign of the charges.
  • Electromagnetic Fields: These are regions where electric and magnetic forces are experienced due to the presence of charged particles. Electromagnetic fields carry energy and can exert forces on other charged particles.
Everyday examples of Maxwell’s electromagnetism
  • When you turn on a light switch, the electric current in the filament of the light bulb produces a magnetic field. This in turn produces an electric field causing the filament to glow white hot.
  • When you listen to the radio, the electromagnetic waves from the radio station interact with the antenna on your radio to produce an electric current. This electric current is then amplified and converted into sound, which you can hear through the speakers on your radio.
  • When you use a microwave oven to heat food, the electromagnetic waves from the microwave oven interact with the water molecules in the food. This causes the water molecules to vibrate, which heats up the food.