Q. A long metallic bar is carrying heat from one of its ends to the other end under steady-state. The variation of temperature $\theta$ along the length $x$ of the bar from its hot end is best described by which of the following figure?
A) [image:11_image6.emf]
B) [image:11_image7.emf]
C) [image:11_image8.emf]
D) [image:11_image8.emf]
Explanation
(b) We know that $\frac{d\mathcal{Q}}{dt} = kA\frac{d\theta}{dx}$
In steady state flow of heat
$d\theta = \frac{d\mathcal{Q}}{dt}.\frac{1}{kA}dx$
$\Rightarrow$ $\theta_{H} - \theta = k'x$
$\Rightarrow$ $\theta = \theta_{H} - k'x$
Equation $\theta = \theta_{H} - k'x$ represents a straight line.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.