CBSE Class 12-science Answered

Quarks are the fundamental constituent of matter and are the elementary entities(particles) that make up the subatomic particles like protons and neutrons.The quarks are assigned fractional electric charges of - 1/3 e (called the down quark, denoted by d) and + 2/3 e (called up quark, denoted by u).The proton is composed of three quarks(i.e.uud), two with charges of +2/3 e and one with charge of -1/3 e, which adds up to a net charge of + e .A neutron is made up of two down quarks and one up quark(ddu). Till now no isolated quark has been observed due to the exceptionally strong force called color force which prevents them from escaping.This force increses with seperation distance.