Physics MCQs for NEET — Practice Questions with Answers

Points to Ponder, point 1, states: 'In considering motion of an object under the gravitational influence of another object the following quantities are conserved: (a) Angular momentum (b) Total mechanical energy. Linear momentum is not conserved'.

Points to Ponder, point 4, clearly states: 'An astronaut experiences weightlessness in a space satellite. This is not because the gravitational force is small at that location in space. It is because both the astronaut and the satellite are in 'free fall' towards the Earth.'

According to the NCERT text, 'An ac generator converts mechanical energy into electrical energy.' and 'In an ac generator, mechanical energy is converted to electrical energy by virtue of electromagnetic induction.'

The NCERT text states, 'The rotation of the coil causes the magnetic flux through it to change, so an emf is induced in the coil.'

The NCERT text mentions, 'When the coil is rotated with a constant angular speed $\omega$, the angle $\theta$ between the magnetic field vector B and the area vector A of the coil at any instant t is $\theta = \omega t$ (assuming $\theta = 0^{\circ}$ at t = 0).'

From the NCERT text, 'the flux at any time t is $\Phi_B = BA \cos \theta = BA \cos \omega t$'.

The NCERT text states, 'Thus, the instantaneous value of the emf is $\varepsilon = NBA \omega \sin \omega t$ (6.19)'.

The NCERT text defines $\varepsilon_0$ as, 'where $NBA \omega$ is the maximum value of the emf... If we denote $NBA \omega$ as $\varepsilon_0$, then $\varepsilon = \varepsilon_0 \sin \omega t$ (6.20)'.

The text states, 'Note from Fig. 6.14 that the emf has its extremum value when $\theta = 90^{\circ}$ or $\theta = 270^{\circ}$, as the change of flux is greatest at these points.'

The NCERT text mentions, 'The ends of the coil are connected to an external circuit by means of slip rings and brushes.'