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Question 15: Name the four fundamental interactions and the particles that mediate each interaction.


Properties of elementary particles can be described by the interacting forces between them. This interaction between the particles is due to the exchange of field particles or quanta.

All particles are subjected to four fundamental forces as described below.

  1. Strong Forces: These are very short range and become negligible for a separation of greater than 10-14 m. they are responsible for binding all protons and neutrons in the nucleus and holds the nucleus together. This is the strongest force in nature. Strong forces are mediated field particles called gluons.
  2. Electromagnetic Force: Electromagnetic force is responsible for binding the atoms and molecules in a substance. Its strength is about 10-2 (one-hundredth) of the strength of the strong force. Electromagnetic force decreases in strength inversely as square of the distance between the interacting particles. Electromagnetic force is mediated by field particles called photons.
  3. Weak Force: The weak force is short-range nuclear force that tends to produce instability in certain nuclei. It is responsible for radioactive decay process. Its strength is about 10-9 times the strength of the strong force. Weak force is mediated by field particle called boson.

Scientists now believe that weak and electromagnetic forces are the manifestation of a single force called electroweak force.

  • Gravitational Force: Gravitational force is long-range force. Its strength is about 10-38 times the strength of the strong force. This force is responsible for holding the planets, stars and galaxies together. This is the weakest force of all forces. It is mediated by field particles called gravitons.

It should be noted that all the four fundamental forces are conservative, t-e, the work done in these fields is independent of the path followed.


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