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# Three Rods of Lengths 20 Cm Each and Area of Cross Section 1 Cm2 Are Joined to Form a Triangle Abc. the Conductivities of the Rods Are Kab = 50 J S−1 M−1°C−1, Kbc = 200 J - Physics

ConceptThermal Expansion of Solids

#### Question

Three rods of lengths 20 cm each and area of cross section 1 cm2 are joined to form a triangle ABC. The conductivities of the rods are KAB = 50 J s−1 m−1°C−1, KBC = 200 J s−1m−1°C−1 and KAC = 400 J s−1 m−1°C−1. The junctions A, B and C are maintained at 40°C, 80°C and 80°C respectively. Find the rate of heat flowing through the rods AB, AC and BC.

#### Solution

Thermal conductivity of rod AB, KAB = 50 J/m-s-°C

Temperature of junction at A, TA = 40°C

Thermal conductivity of rod BC, KBC = 200 J/m-s-°C

Temperature of junction at B, TB = 80°C

Thermal conductivity of rod BCKCA = 400 J/m-s-°C

temperature of junction at CTC = 80°C

l = 20 cm = 20 × 10−2 m

A = 1 cm2 = 10−4 m2

(a) (DeltaQ)_{AB}/(Deltat) = (K_{AB^A}(T_B - T_A))/l

=( 50 xx1xx10^-4 (40))/(20xx10^-2)

= 1 W

(b) (DeltaQ_{AC})/(Deltat) =( K_{AC^-A}(T_C - T_A))
/(20xx10^2)

= 8 w

( c ) (DeltaQ)_{BC)/ (Deltat) = ((K_{BC})^6A(T_B - t_c))/l

= 0

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#### APPEARS IN

Solution Three Rods of Lengths 20 Cm Each and Area of Cross Section 1 Cm2 Are Joined to Form a Triangle Abc. the Conductivities of the Rods Are Kab = 50 J S−1 M−1°C−1, Kbc = 200 J Concept: Thermal Expansion of Solids.
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