Electromagnetism

The Basics of Electromagnetism

  • Electromagnetism is a branch of physics involving the study of the electromagnetic force.
  • This force is a type of physical interaction that occurs between electrically charged particles.
  • The electromagnetic force is one of the four fundamental forces and exhibits electromagnetic fields such as electric fields, magnetic fields, and light.

Electromagnetic Fields

  • An electromagnetic field (EM field) is generated when charged particles such as electrons are accelerated.
  • All electromagnetic waves travel at the speed of light in a vacuum, including light itself which is an electromagnetic wave.
  • EM fields can exert force on other charged particles through the electromagnetic force.

The Electromagnetic Spectrum

  • The electromagnetic spectrum is the range of all types of EM radiation.
  • Radiation is energy that travels and spreads out as it goes - visible light that comes from a lamp in your house or radio waves that come from a radio station are two types of electromagnetic radiation.
  • Other examples of electromagnetic radiation include microwaves, infrared and ultraviolet light, X-rays and gamma rays.
  • The various types of waves are categorised on the basis of their frequencies and wavelengths into the electromagnetic spectrum.

Principles of Electromagnetism

  • Electromagnetism involves the interaction of electric and magnetic fields.
  • A moving electric charge generates a magnetic field, while a changing magnetic field can produce an electric field.
  • These effects happen across a wide array of frequencies, including those of visible light and other forms of electromagnetic radiation.
  • This is described by Faraday’s Law, which states that a changing magnetic field produces an electric field; and Ampere’s Law, stating a current or changing electric field produces a magnetic field.

Transformation of Energy in Electromagnetism

  • Electromagnetic energy can be transformed into other forms of energy.
  • For instance, when sunlight - a form of electromagnetic energy - strikes a solar panel, it is converted into electrical energy.
  • Similarly, microwaves in a microwave oven turn into thermal energy heating up your food.

Applying Electromagnetism

  • Electromagnetism has a wide variety of applications.
  • In transformers and generators, electricity is generated by the motion of conductors in a magnetic field through electromagnetic induction.
  • Devices like televisions, cell phones, and computers work by manipulating electromagnetic waves.
  • MRI (Magnetic Resonance Imaging) scanners use strong magnetic fields and radio waves to create detailed images of the body.

Electromagnetic Induction

  • Electromagnetic induction is the process of generating an electromotive force (EMF) or voltage across a conductor when it is exposed to a varying magnetic field.
  • This principle was discovered by Michael Faraday who formulated the first law of electromagnetic induction.
  • Faraday’s law of electromagnetic induction states that the EMF induced in a circuit is proportional to the rate of change of flux through the circuit.

Behaviour of Charges in Electromagnetic Fields

  • Charges in electromagnetic fields obey the Lorentz force law.
  • The Lorentz force law explains how a particle of charge ‘q’ moving with a velocity ‘v’ in a magnetic field ‘B’ experiences a force ‘F’.
  • This force is given by the cross product F = qv × B, and its direction is normal (perpendicular) to both the velocity of the charge and the magnetic field.
  • This force causes the particle to move in a circular path if it enters the magnetic field at a certain angle.