Question

Two rods of equal length and diameter have thermal conductivities $3$ and $4$ units respectively. If they are joined in series, the thermal conductivity of the combination would be

• A. $3.43$
• B. $2.53$
• C. $5.43$
• D. $4.43$

Answer 1

Answer: (A)

$3.43$

As we know that both rods are joined in series, so equivalent thermal conductivity will be $K_1+K_2$

Now, we know that

$R=\frac{L}{KA}$

So,

$\frac{2L}{K_{equivalent}}=\frac{L}{K_1}+\frac{L}{K_2}$

$\frac{2L}{K_{equivalent}}=\frac{L}{3}+\frac{L}{4}$

$K_{equivalent}=\frac{24}{7}$

$K_{equivalent}=3.43$

Thus option A is correct.