Question

please tell me answer ....​

Answer 1

Answer:

Given:

2 tubes are connected in series . One cylinder is of silver and the other is of Aluminum.

Thermal conductivity of

• Ag =K
• Al = K/5

To find:

Effective thermal conductivity

Concept:

We will use analogy of Thermal resistance with Electric resistance.

Here the blocks have resistances which are placed in series.

Formulas used:

Thermal resistance = L/KA ,

where L = length , K = thermal conductivity and A = area of cross section.

Calculation:

Let resultant Thermal conductivity be K"

Since the resistances are in series, hence:

R eq. = R1 + R2

=> 2L/(K"A) = L/(KA) + L/(KA/5)

=> 2L/(K"A) = L/(KA) + 5L/(KA)

=> 2/K" = 1/K + 5/K

=> 2/K" = 6/K

=> K" = K/3

So the final answer is option C)

Answer 2

$\large{\orange{\underline{\red{\mathscr{FORMULA \: \: USED:-}}}}}$

thermal resistance =L/KA.

L IS LENGTH, k is thermal conductivity.

a is a area.

$\huge{\orange{\underline{\red{\mathscr{ANSWER:-}}}}}$

resultant thermal conductivity is k'.

THE RESISTANCE ARE IN SERIES.

R eq. =R1+R2

=2l/(k'A) =l/(kA)+l/(kA/5)

=2l/(k'A) =l/(kA) +5l(kA)

2/k'=1/k+5k

2/k'=6k

k'=k/3.

.°. option c is the right answer.

$\huge{\orange{\underline{\red{\mathscr{THANKS.}}}}}$