Comparison

This is known as Coulomb force.

where is attractive it charges are of opposite nature (one positive and the other negative) Otherwise, it is repulsive Charges in motion produce magnetic effects and a magnetic field gives rise to a force on a moving charge. Electric and magnetic effects are inseparable, hence the name electromagnetic force. Electrical repulsion between two protons at a given distance is 10" omes stronger than ther gravitational attractive force Like gravitational force, it acts over large distances and does not require a medium but its magnitude changes on changing the medium. It governs the structure of atoms and molecules, the dynamics of chemical reactions and the mechanical, thermal and other properties of materials. The macroscopic forces like friction, tension etc. are derived as the result of electromagnetic forces between atoms or molecules

Some of the properties of electromagnetic forces are:

(1) They are govered by Coulomb's law.

() They may be attractive or repulsive

() They are central forces

(v) They obey inverse square law.

They are conservative forces.

() They are mediated by the particle called photon

Strong nuclear forces

3 : It is the force which binds nucleons (protons and neutrons) in a nucleus Nucleus contains positively charged protons and electrically neutral neutrons Repulsive electrostatic force between protons should make a nucleus unstable. There should be a strong attractive force that counteracts the repulsive force to keep a nucleus stable We know that gravitational force is negligible as compared to the electrostatic force. So, we have a new basic force, Le., strong nuclear force, which is the strongest of all fundamental forces, about 100 times the electromagnetic force. It is same between a proton and a neutron, a proton and a proton, a neutron and a neutron. It is an extremely short ranged force (-10-15 m) it keeps the nucleus stable. It does not depend upon charge. Electron does not experience

this force.

You will learn in higher classes that protons and neutrons are made up of more elementary constituents called quarks. We are normally not aware of huclear forces as we do not come across bare nuclei in. daily life. However, the phenomena like nuclear fission/fusion etc. involve these forces.

of the important properties are:

() They are charge independent.

(i) They are the strongest forces- 100 times stronger than electrostatic force, 1013 times stronger tha weak nuclear force, 10 times stronger than gravitational force.

(i) They have the short range, ... upto distances of the order of 10-15 m. ~ | firmad

(v) They are basically attractive forces. However, when distance between nucleons is less than O fermi, they become repulsive.

M They are non-central forces.

(M) They are non-conservative forces.

(vi) They do not obey inverse square law.

(vi) They are mediated by the particle 'pi-meson.