Smoke is an example of ...

The differential equation of all circles which pass through the origin and whose centres lie on the $Y$-axis is

$A$ piece of copper and another of germanium are cooled from room temperature to $80\, K$. The resistance of :

The $H-$ zone in the skeletal muscle fibre is due to:

Let $a, b \in R$. If the mirror image of the point $P(a, 6, 9)$ with respect to the line $\frac{x-3}{7} = \frac{y-2}{5} = \frac{z-1}{-9}$ is $(20, b, -a-9)$,then $|a+b|$ is equal to:

In a nuclide,one $a.m.u.$ of mass is dissipated into energy to bind its nucleons. The energy equivalent of this mass is