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What role does gravity play in natural convection?
The NCERT text says, 'In natural convection, gravity plays an important part.' This is because density differences due to heating lead to buoyant forces, and gravity acts on these density differences, causing the less dense (hotter) fluid to rise and denser (colder) fluid to sink.
Convection involves what type of heat transport?
The NCERT text clarifies, 'Convection involves bulk transport of different parts of the fluid.' This contrasts with conduction (molecular collisions) and radiation (electromagnetic waves).
Why does the ground heat up more quickly than large bodies of water during the day, contributing to sea breezes?
The NCERT text explains, 'During the day, the ground heats up more quickly than large bodies of water do. This occurs both because water has a greater specific heat capacity and because mixing currents disperse the absorbed heat throughout the great volume of water.'
Which mode of heat transfer is essentially characterized by the movement of heated material itself?
Convection is defined as the mode of heat transfer by the actual motion of matter, which is the movement of the heated material itself. Conduction involves molecular vibrations without bulk movement, and radiation involves electromagnetic waves.
Which of the following statements about convection is INCORRECT?
The NCERT text states, 'Conduction and convection require some material as a transport medium. These modes of heat transfer cannot operate between bodies separated by a distance in vacuum.' Radiation, not convection, can occur in a vacuum.
A transverse wave is incident on a rigid boundary. What is the phase change experienced by the reflected wave?
According to the provided text, 'A travelling wave, at a rigid boundary or a closed end, is reflected with a phase reversal but the reflection at an open boundary takes place without any phase change.' A phase reversal corresponds to a phase change of $\pi$ or $180^\circ$.
Which of the following phenomena is an example of reflection by a rigid boundary?
The text states, 'The phenomenon of echo is an example of reflection by a rigid boundary.' Echo occurs when sound waves reflect off a hard surface, which acts as a rigid boundary.
When a wave is reflected from a rigid boundary, how does the shape of the reflected wave compare to the incident wave, assuming no absorption of energy?
The text mentions, 'the reflected wave has the same shape as the incident pulse but it suffers a phase change of $\pi$ or $180^\circ$ on reflection' when meeting a rigid boundary.
For an incident travelling wave $y_i(x, t) = a \sin (kx - \omega t)$, what is the expression for the reflected wave at a rigid boundary?
The text states, 'For an incident wave $y_i(x, t) = a \sin (kx - \omega t)$ the reflected wave at a rigid boundary is $y_r(x, t) = -a \sin (kx + \omega t)$'.
What happens to the displacement at a rigid boundary when a wave is reflected?
The text explains regarding rigid boundaries, 'the disturbance must have zero displacement at all times at the boundary. By the principle of superposition, this is possible only if the reflected and incident waves differ by a phase of $\pi$, so that the resultant displacement is zero.'
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.