Fundamental forces

In physics, fundamental forces cannot be explained through simpler or more elementary interactions, so are regarded as fundamental building blocks of the natural world.

The four fundamental forces that account for all the forms of pulling and pushing between things are:

Electromagnetic force

• The electromagnetic force is the interaction that arises between electrically charged particles, such as electrons and is characterized by positive or negative charges. Oppositely charged particles exert an attractive force, while particles with the same charge exert a repulsive force. Photons carry electromagnetic force through electric and magnetic fields, propagating at the speed of light.

Weak Nuclear force

• In nuclear physics and particle physics, the weak nuclear force mediates interactions between subatomic particles and is responsible for radioactive decay in atoms. The weak nuclear force doesn’t affect electromagnetic radiation.

Strong Nuclear force

• The strong nuclear force binds matter together and is responsible for holding together protons and neutrons which are the subatomic particles within the atomic nucleus. It counteracts repulsive electromagnetic forces that push subatomic particles apart but only operate over the smallest imaginable distances. The strong nuclear force plays a central role in storing the energy that is used in nuclear power and nuclear weapons.

Gravitational force

• Gravity is the phenomenon that attracts objects with mass or energy towards one another. It affects celestial bodies such as planets, stars, galaxies, and even light. The influence of gravity on smaller objects like human beings in the presence of larger ones, such as planets, is evident. Gravity, such as the Moon’s gravity, leads to ocean tides on Earth. Gravity accounts for the weight of physical objects. Its range is infinite, although its effects weaken as objects move farther apart.

Electromagnetism is the fundamental force that governs the behaviour of electric and magnetic fields. It encompasses the generation, interaction, and propagation of these fields as electromagnetic waves, and includes the principles and phenomena related to these interactions.

In its broadest sense, electromagnetism refers to the entire realm of phenomena arising from the fundamental electromagnetic force. This includes:

• The electromagnetic force itself: The interaction between electrically charged particles, causing attraction or repulsion.
• Electromagnetic fields: Invisible fields associated with charged particles and currents, exerting forces on other charged particles.
• Electromagnetic radiation: Energy travelling in the form of waves or particles (photons), such as light, radio waves, and X-rays.

• Find out more about electromagnetism here.

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.