Q. A liquid in a beaker has temperature $\theta(t)$ at time $t$ and $\theta_{0}$ is temperature of surroundings, then according to Newton’s law of cooling the correct graph between $\log_{e}{(\theta - \theta_{0})}$ and $t$ is

A) [image:11_image40.emf]
B) [image:11_image41.emf]
C) [image:11_image42.emf]
D) [image:11_image43.emf]
Explanation

(a) $\frac{d\theta}{dt} = - k(\theta - \theta_{0})$
$\int_{\theta_{0}}^{\theta}{\frac{d\theta}{\theta - \theta_{0}} = - k\int_{0}^{t}{dt}}$
$\ln{\left( \theta - \theta_{0} \right) = - kt + C}$
So graph is straight line
[image:11_image67.emf]

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.