An iron rod is placed parallel to a magnetic field of intensity $2000 \ A \ m^{-1}$. The magnetic flux through the rod is $6 \times 10^{-4} \ Wb$ and its cross-sectional area is $3 \ cm^2$. The magnetic permeability of the rod in $Wb \ A^{-1} \ m^{-1}$ is:

When the angle of incidence is $60^{\circ}$ on the surface of a glass slab,it is found that the reflected ray is completely polarized. The velocity of light in glass is

Which scientist proposed the theory of continuity of germplasm?

$A$ wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to the current,the temperature of the wire is raised by $\Delta T$ in time $t$. $N$ number of similar cells is now connected in series with a wire of the same material and cross section but of length $2L$. The temperature of the wire is raised by the same amount $\Delta T$ in the same time $t$. The value of $N$ is:

Two loops $P$ and $Q$ are made from a uniform wire. The radii of $P$ and $Q$ are $r_1$ and $r_2$ respectively. Their moments of inertia are $I_1$ and $I_2$ respectively. If $I_2/I_1 = 4$,then $r_2/r_1 = ?$

$A$ ball of mass $1.2 \ kg$ moving with a velocity of $12 \ ms^{-1}$ makes a one-dimensional collision with another stationary ball of mass $1.2 \ kg$. If the coefficient of restitution is $\frac{1}{\sqrt{2}}$,then the ratio of the total kinetic energy of the balls after collision to the initial kinetic energy is: