Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
Concepts Of Physics MCQ Edition [Volume 2]PhysicsHeat Transfer

A calorimeter holds 50 g of water at 50^ C , and its temperature drops to 45^ C in 10 minutes. If the calorimeter instead holds 100 g of water at 50^ C , the temperature takes 18 minutes to reach 45^ C . Determine the water equivalent of the calorimeter.

Options

  1. A25 g
  2. B12.5 g
  3. C6.25 g
  4. D10 g

Correct answer

B. 12.5 g

Step-by-step solution

According to Newton's law of cooling, the time t taken to cool through a given temperature range is directly proportional to the total heat capacity of the system. t (m + W) where m is the mass of water and W is the water equivalent of the calorimeter. For the two cases, we can write the ratio of the times taken as: t₁ t₂ = m₁ + W m₂ + W Substituting the given values: 10 18 = 50 + W 100 + W 5 9 = 50 + W 100 + W 5(100 + W) = 9(50 + W) 500 + 5W = 450 + 9W 4W = 50 W = 12.5 g

Practice Heat Transfer on Quantrex Academy →

More from Heat Transfer

A liquid-nitrogen container is constructed from a 1 -cm thick styrofoam sheet with a thermal conductivity of 0.025 J s ⁻¹ m ⁻¹ ^ C ⁻¹ . Liquid nitrogen at 80 K is stored inside. A A uniform slab measuring 10 cm 10 cm 1 cm is placed between two heat reservoirs maintained at temperatures of 10^ C and 90^ C . The larger surface areas of the slab are in contact A person's normal body-temperature is 97 ^ F . Determine the rate at which heat flows out of their body through the clothes, assuming the following values: room temperature = 47 ^ A steel rod ( K = 46 J s ⁻¹ m ⁻¹ ^ C ⁻¹ ) of length 1.0 m has one end kept in ice at 0^ C and the opposite end in boiling water at 100^ C . The rod has a cross-sectional area of 0.An icebox almost entirely filled with ice at 0^ C is submerged in a large volume of water at 20^ C . The walls of the box have a surface area of 2400 cm ^2 , a thickness of 2.0 mm Water is boiled in a container whose bottom has a surface area of 25 cm ^2 , a thickness of 1.0 mm , and a thermal conductivity of 50 W m ⁻¹ ^ C ⁻¹ . After boiling begins, 100 g ofA pitcher having 1 -mm thick porous walls holds 10 kg of water. Water reaches the outer surface and evaporates at a rate of 0.1 g s ⁻¹ . The surface area of the pitcher (one side) Forming three sides of a square, a steel frame ( K = 45 W m ⁻¹ ^ C⁻¹ ) has a total length of 60 cm and a cross sectional area of 0.20 cm ^2 . The two free ends are maintained at 20 Full Heat Transfer list All Concepts Of Physics MCQ Edition [Volume 2] PYQs