In which year was the first successful cotton mill established in India?

$I-V$ characteristic of a copper wire of length $L$ and area of cross-section $A$ is shown in figure. The slope of the curve becomes

Obtain the expression for the fringe width of interference fringes in Young's Double slit experiment.

Derive the expression for the intensity at a point where interference of light occurs. Arrive at the conditions for maximum and zero intensity.

Find the resistivity of the material of a metallic conductor of length $2 \mathrm{m}$ and area of cross-section $1.4\times {10}^{-6} {\mathrm{m}}^2$. The resistance of the conductor is $0.04 \mathrm{ohm}$.

Write the relationship between electrical resistance and electrical resistivity for a metallic conductor of cylindrical shape. Hence, derive the SI unit of electrical resistivity.

Two charges of equal magnitudes and at a distance $r$ exert a force $F$ on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is