Physics MCQs for NEET — Practice Questions with Answers

The NCERT clearly states under 'EXERCISES', '(a)You can shield a charge from electrical forces by putting it inside a hollow conductor. Can you shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means ?' and later, 'Gravitational shielding is not possible.' This highlights the difference between gravitational and electrical forces in this regard.

From 'POINTS TO PONDER' (Point 1 on page 151): 'A satisfactory understanding of magnetic phenomenon in terms of moving charges/currents was arrived at after 1800 AD. But technological exploitation of the directional properties of magnets predates this scientific understanding by two thousand years.'

Referring to the 'POINTS TO PONDER' table (page 151), the unit for Magnetic intensity (H) is listed as A m$^{-1}$. Also, on page 146, it states that H is measured in units of A m$^{-1}$.

From 'POINTS TO PONDER' (Point 6 on page 152): 'Diamagnetism is universal. It is present in all materials. But it is weak and hard to detect if the substance is para- or ferromagnetic.'

The context states: 'Here $\alpha_V$ is also a characteristic of the substance but is not strictly a constant. It depends in general on temperature (Fig 10.6). It is seen that $\alpha_V$ becomes constant only at a high temperature.' Therefore, option 3 is incorrect.

The context states: 'If the substance is in the form of a long rod, then for small change in temperature, $\Delta T$, the fractional change in length, $\Delta l/l$, is directly proportional to $\Delta T$. where $\alpha_l$ is known as the coefficient of linear expansion (or linear expansivity)...'

The context explicitly states: 'The relation between them is : $\alpha_V = 3\alpha_l$'.

From Table 10.1, $\alpha_l$ for Glass (pyrex) is $0.32 \times 10^{-5} K^{-1}$ and for Copper is $1.7 \times 10^{-5} K^{-1}$. Comparing these, $1.7 / 0.32 \approx 5.3$, so copper expands about five times more than glass.

The context defines this phenomenon: 'What happens by preventing the thermal expansion of a rod by fixing its ends rigidly? Clearly, the rod acquires a compressive strain due to the external forces provided by the rigid support at the ends. The corresponding stress set up in the rod is called thermal stress.'

The context mentions: 'Similarly, in case of gases, a balloon partially inflated in a cool room may expand to full size when placed in warm water.' This describes the volume expansion of the air (a gas) inside the balloon.