PHYSICS

QUESTION: A vibrating tuning fork when held against the surface of a table produces a loud sound.  Give reason. ANSWER: A vibrating tuning fork forces the table top to vibrate. As the table top has large surface area, amplitude of vibration increases. 

QUESTION: What are superconductors? ANSWER: The materials whose resistivity is zero at very low temperature is called superconductors. Example: Mercury below 4K.

QUESTION: A satellite revolves around a planet in a circular orbit. What is the work done by the satellite at any instant? Answer: The work done is zero.  As the Centripetal force by the satellite is perpendicular to the displacement of the body.

QUESTION: Why is it  not advisable to use a piece of copper wire as fuse wire in an electric circuit.? ANSWER: Fuse wire should have low melting point and high resistivity but copper has high melting point and low resistivity. 

Question: Why does a stone lying in the sun get heated up much more than water lying for the same duration of time? Answer: The specific heat capacity of  stone is less than the that of  water.