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

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Heat Transfer

A composite slab is formed by pasting together two plates of...

A composite slab is formed by pasting together two plates of thicknesses L1L_1 and L2L_2 and thermal conductivities K1K_1 and K2K_2. The slabs possess equal cross-sectional area. Determine the equivalent conductivity of the composite slab.

Options

  1. AK1L2+K2L1L1+L2\dfrac{K_1 L_2 + K_2 L_1}{L_1 + L_2}
  2. BK1K2(L1+L2)L1K1+L2K2\dfrac{K_1 K_2 (L_1 + L_2)}{L_1 K_1 + L_2 K_2}
  3. CK1L1+K2L2L1+L2\dfrac{K_1 L_1 + K_2 L_2}{L_1 + L_2}
  4. DK1K2(L1+L2)L1K2+L2K1\dfrac{K_1 K_2 (L_1 + L_2)}{L_1 K_2 + L_2 K_1}

Correct answer

D. K1K2(L1+L2)L1K2+L2K1\dfrac{K_1 K_2 (L_1 + L_2)}{L_1 K_2 + L_2 K_1}

Step-by-step solution

For a composite slab connected in series, the equivalent thermal resistance is the sum of the individual thermal resistances.

Req=R1+R2R_{eq} = R_1 + R_2

Using the formula for thermal resistance R=LKAR = \dfrac{L}{KA}, where AA is the cross-sectional area:

L1+L2KeqA=L1K1A+L2K2A\dfrac{L_1 + L_2}{K_{eq} A} = \dfrac{L_1}{K_1 A} + \dfrac{L_2}{K_2 A}

L1+L2Keq=L1K2+L2K1K1K2\dfrac{L_1 + L_2}{K_{eq}} = \dfrac{L_1 K_2 + L_2 K_1}{K_1 K_2}

Keq=K1K2(L1+L2)L1K2+L2K1K_{eq} = \dfrac{K_1 K_2 (L_1 + L_2)}{L_1 K_2 + L_2 K_1}
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… Concepts Of Physics MCQ Edition [Volume 2]A uniform slab measuring 10 cm × 10 cm × 1 cm is placed between two heat reservoirs… Concepts Of Physics MCQ Edition [Volume 2]A person's normal body-temperature is 97 ^ ^ ^ ∘ F . Determine the rate at which heat… Concepts Of Physics MCQ Edition [Volume 2]A steel rod ( K = 46 J s^ -1 m^ -1 ^ ^ ^ ∘ ^ -1 ) of length 1.0 m has one end kept in ice… Concepts Of Physics MCQ Edition [Volume 2]An icebox almost entirely filled with ice at 0^ ^ ^ ∘ C is submerged in a large volume of… Concepts Of Physics MCQ Edition [Volume 2]Water is boiled in a container whose bottom has a surface area of 25 cm^2 , a thickness… Concepts Of Physics MCQ Edition [Volume 2]A pitcher having 1-mm thick porous walls holds 10 kg of water. Water reaches the outer… Concepts Of Physics MCQ Edition [Volume 2]Forming three sides of a square, a steel frame ( K = 45 W m^ -1 ^ ^ ^ ∘ C^ -1 ) has a… Concepts Of Physics MCQ Edition [Volume 2] Full Heat Transfer list All Concepts Of Physics MCQ Edition [Volume 2] PYQs