Question

A heater is supplying heat at the rate of $6000\mathrm{J}/\min$. If power produced by gas is $90\mathrm{W}.$ Find the time taken to increase internal energy by $2.5\times {10}^3\mathrm{J}?$

• A. $250\mathrm{s}$
• B. $150\mathrm{s}$
• C. $500\mathrm{s}$
• D. $100\mathrm{s}$

Answer 1

The correct option is A

$250\mathrm{s}$

The explanation for correct option:

$$\begin{gathered} △\mathrm{U}=\mathrm{Q}–\mathrm{w} \\ 2500=100\mathrm{t}–90\mathrm{t} \\ \mathbf{}\mathbf{}\mathbf{t}\mathbf{}\mathbf{}\mathbf{=}\mathbf{}\mathbf{250}\mathbf{}\mathbf{s} \\ \mathrm{Hence},\mathrm{the}\mathbf{time}\mathbf{}\mathbf{taken}\mathbf{}\mathrm{to}\mathrm{increase}\mathrm{the}\mathrm{internal}\mathrm{energy}\mathrm{is}\mathbf{250}\mathbf{}\mathbf{s}\mathbf{.} \end{gathered}$$

The explanation for incorrect options :

Options B, C and D have incorrect values for the time taken.

Therefore, option A is correct.