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21. A marble title would feel cold as compared to a wooden tile on a winter morning, because the marble tile ______.
A. Is a better conductor of heat than the wooden tile.
B. Is polished while wooden tile is not polished.
C. Reflects more heat than wooden tile.
D. Is a poor conductor of heat than the wooden tile.
ANSWER:A
SOLUTION :The ‘marble tile’ is a good conductor of heat as compared to the ‘wooden tile’.
22. What determines the colour of star ?
A. Distance
B. Radius
C. Temperature
D. None
ANSWER:C
SOLUTION:Convection can only take place through fluids i.e. liquids and gases. Solids cannot transfer heat through convection.
23. Burns cause by steam are much more irritated than those caused by boiling water because ?
A. Steam has latent heat
B. Temperature of steam is higher
C. Steam is a gas & engulf the body quickly
D. None
ANSWER:A
SOLUTION:Steam causes more severe burns than boiling water at the same temperature because steam has more heat energy.
24. In an earthen pitcher, the water remains cold due to the process of ?
A. Condensation
B. Sublimation
C. Evaporation
D. None
ANSWER:C
SOLUTION:The process of conversion of a liquid into its vapors at room temperature is called evaporation. The temperature at which the water starts evaporating is known as latent heat of vaporization.
25. When a bottle is filled with water & it is freezing,the bottle breaks down because?
A. Water expand on heating
B. Water expand upon freezing
C. Bottle shrinks at freezing point
D. None
ANSWER:B
SOLUTION:When a bottle is filled with water and frozen, the bottle breaks because water expands when it freezes. Water expands nearly 9% when it reaches its freezing point, but the bottle continues to contract. Since the water has no space to expand, the bottle breaks.
26. Which of the following is the fastest process of heat transfer?
A. Conduction
B. Convection
C. Radiation
D. None
ANSWER:C
SOLUTION :Radiation is the fastest method of heat transfer because it occurs at the speed of light and doesn’t require a medium to travel. Heat is transferred in the form of electromagnetic waves, and radiation can even transfer energy in a vacuum.
27. A cooking pot is coated black because?
A. Black substances absorb more heat
B. Black surfaces are easier to clean
C. Black substances reflect more heat
D. None
ANSWER:A
SOLUTION:Cooking pots are often painted black on the bottom because black substances absorb more heat, which speeds up the cooking process.
28. At what temperature are the Celsius & Fahrenheit equal ?
A. +40
B. – 40
C. 0
D. +100
ANSWER:B
SOLUTION: There are two important temperature scales, Celsius and Fahrenheit used in the world. There is a point on both scales where the temperatures in degrees are equal. This is – 40 ° C and – 40 ° F .
29. In which of the following processes of heat transfer no medium is required?
A. Conduction
B. Convection
C. Radiation
D. None
ANSWER:C
SOLUTION: Radiation is the only process of heat transfer that does not require a medium. In radiation, heat is transferred in the form of electromagnetic waves that can travel through a vacuum. This is how heat from the sun reaches Earth’s surface.
30. The best & poorest conductor of heat are respectively?
A. Copper & gold
B. Silver & gold
C. Copper & aluminium
D. Silver & lead
ANSWER:D
SOLUTION:Silver (Ag) is the best conductor of heat, and lead (Pb) is the poorest. Metals are heat conductors because of the free movement of their electrons, which transfer heat as they bump into each other.