Physics MCQs for NEET — Practice Questions with Answers

The NCERT states, 'This model was picturesquely called plum pudding model of the atom.' and also directly attributes this description to Thomson's model: 'Thomson in 1898 proposed that an atom consists of uniform sphere of positive electricity with electrons embedded into it. This model in which mass of the atom is considered to be evenly spread over the atom...'

The exercise question implies this: 'In the ground state of __________ electrons are in stable equilibrium, while in __________ electrons always experience a net force.' The correct choice for stable equilibrium is Thomson's model, where electrons are statically embedded. In Rutherford's model, electrons are constantly accelerating, experiencing a net force.

The NCERT text says, 'Rutherford’s model of atom resembles the solar system in which the nucleus plays the role of sun and the electrons that of revolving planets.'

The NCERT states, 'Further, it was also silent about the electronic structure of atoms i.e., about the distribution and relative energies of electrons around the nucleus. The difficulties of the Rutherford model were overcome by Niels Bohr in 1913 in his model of the hydrogen atom.'

The NCERT explicitly mentions, 'According to this model, the positive charge of the atom is uniformly distributed throughout the volume of the atom and the negatively charged electrons are embedded in it like seeds in a watermelon.'

The NCERT summary states, 'In Rutherford’s model, most of the mass of the atom and all its positive charge are concentrated in a tiny nucleus (typically one by ten thousand the size of an atom)'.

Under Rutherford's nuclear model description in NCERT, point (iii) states: 'Electrons and the nucleus are held together by electrostatic forces of attraction.'

The NCERT text states, 'Towards the end of the nineteenth century, it was proved experimentally that atoms are divisible and consist of three fundamental particles: electrons, protons and neutrons.' This led to the need for atomic models like Thomson's and Rutherford's.

The NCERT highlights this as a major difficulty: 'It predicts that atoms are unstable because the accelerated electrons revolving around the nucleus must spiral into the nucleus. This contradicts the stability of matter.'

According to the NCERT text, 'The latent heat of fusion (Lf) is the heat per unit mass required to change a substance from solid into liquid at the same temperature and pressure. The latent heat of vaporisation (Lv) is the heat per unit mass required to change a substance from liquid to the vapour state without change in the temperature and pressure.' This clearly indicates that latent heat is associated with a change of state at constant temperature.