Physics MCQs for NEET — Practice Questions with Answers

The text mentions: 'A most natural explanation of the observations was that heat was a form of energy and the experiment demonstrated conversion of energy from one form to another–from work to heat.' It also noted that 'the amount of heat produced depended on the work done... but not on the sharpness of the drill' contradicting the caloric theory.

The context states: 'Thus, it includes only the (disordered) energy associated with the random motion of molecules of the system.'

The context asks: 'how to assign numerical values to temperatures of different bodies ? In other words, how do we construct a scale of temperature ? Thermometry deals with this basic question...'

The context states: 'The distinction between mechanics and thermodynamics is worth bearing in mind. In mechanics, our interest is in the motion of particles or bodies under the action of forces and torques. Thermodynamics is not concerned with the motion of the system as a whole. It is concerned with the internal macroscopic state of the body.'

As per the NCERT text, 'An important feature of this model is that the mass of the atom is assumed to be uniformly distributed over the atom.' This is in contrast to Rutherford's model where mass is concentrated in the nucleus.

The NCERT states, 'A classical atom based on Rutherford’s model is doomed to collapse.' This is because electrons revolving around the nucleus are accelerating and, according to classical electromagnetism, should continuously radiate energy and spiral into the nucleus, thus experiencing a net force.

According to the NCERT summary for Rutherford's model: 'most of the mass of the atom and all its positive charge are concentrated in a tiny nucleus'.

The NCERT states, 'This model in which mass of the atom is considered to be evenly spread over the atom was proved wrong by Rutherford’s famous alpha-particle scattering experiment in 1909.' Rutherford's experiment indicated a highly non-uniform distribution with a central, dense nucleus.

The NCERT chapter 'Atoms' summary explicitly mentions Rutherford nuclear model's 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.'

The exercise question asks: 'The size of the atom in Thomson’s model is .......... the atomic size in Rutherford’s model. (much greater than/no different from/much less than.)'. The answer given in the context (implied by the solution of such questions) is 'no different from'. While the internal structure differs, both models attempt to describe the overall size of the atom as roughly $10^{-10}$ m.