In which process the rate of transfer of heat is maximum?

• Conduction

• Radiation

• Convection

• In all three heat is transferred with the same speed

According to Newton's law of cooling, the rate of cooling of a body is proportional to (Δθ)ⁿ, where Δθ is the difference of the temperature of the body and the surroundings, and n is equal to

• 2

• 3

• 4

• 1

A cup of tea having the temperature 80°C is kept in a room,which is at 20°C. Which of the given curves best represents the variation of temperature T of the cup with time t ?

An ice box made of Styrofoam (thermal conductivity = 0.01 Jm^-1s^-1K) is used to keep liquids cool. It has a total wall area including lid of 0.8 m² and wall thickness of 2.0 cm. A bottle of water is placed in the box and filled with ice. If the outside temperature is 30°C, the rate of flow of, heat into the box is (in Js^-1)

• 16

• 14

• 12

• 10

5 g of ice of O°C is dropped in a beaker containing 20 g of water at 40°C. The final temperature will be

• 32°C

• 16°C

• 8°C

• 24°C

An electric heater of resistance 6 Ω works for 10 min on a 60 V line. The energy liberated in this period of time is

• 7.2 × 10³ J

• 3.6 × 10⁵ J

• 43.2 × 10⁴ J

• 28.8 × 10⁴ J

197.

Colour of a star indicates its

• density

• distance

• energy

• temperature

Which of the following has maximum specific heat?

• Water

• Alcohol

• Glycerene

• Oil

Value of - 40°C in Fahrenheit scale is

• - 40F

• 32 F

• - 32 F

• 40°C

The amount of heat required to change 1 g (0°C) of ice into water of 100°C, is

• 716 cal

• 500 cal

• 180 cal

• 100 cal