MHT CET · Physics · Thermal Properties of Matter
Two rods of same length and material are joined end to end. They transfer heat in 8 second. When they are joined in parallel they transfer same amount of heat in same conditions in time
- A 3 s
- B 2 s
- C 1 s
- D 4 s
Answer & Solution
Correct Answer
(B) 2 s
Step-by-step Solution
Detailed explanation
Let \(R\) be the thermal resistance of each rod when connected in series, the total resistance will be \(\mathrm{R}_{\mathrm{s}}=2 \mathrm{R}\)
Whey they are connected in parallel, the effective resistance will be
\(
\begin{aligned}
& \mathrm{R}_{\mathrm{p}}=\frac{\mathrm{R}}{2} \\
& \therefore \frac{\mathrm{R}_{\mathrm{p}}}{\mathrm{R}_{\mathrm{s}}}=\frac{1}{4}
\end{aligned}
\)
In parallel combination, the resistance becomes one-fourth and hence time will also become one-fourth.
\(\therefore\) Time taken \(\frac{8}{4}=2 \mathrm{~s}\)
Whey they are connected in parallel, the effective resistance will be
\(
\begin{aligned}
& \mathrm{R}_{\mathrm{p}}=\frac{\mathrm{R}}{2} \\
& \therefore \frac{\mathrm{R}_{\mathrm{p}}}{\mathrm{R}_{\mathrm{s}}}=\frac{1}{4}
\end{aligned}
\)
In parallel combination, the resistance becomes one-fourth and hence time will also become one-fourth.
\(\therefore\) Time taken \(\frac{8}{4}=2 \mathrm{~s}\)
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