Who first discovered lichens?

The potential difference across the terminals of the battery shown in the figure is ............ $V$. ($r$ = internal resistance of the battery)

The $P-V$ diagram of a diatomic gas is a straight line passing through the origin. The molar heat capacity of the gas in the process will be:

Which carbohydrate is used in the silvering of mirrors?

Two stars of masses $M$ and $2M$ are at a distance $d$ apart and are revolving around their common center of mass. The angular velocity of the system of two stars is ($G$ is the universal gravitational constant):

Water is conveyed through a uniform tube of $8 \text{ cm}$ in diameter and $3140 \text{ m}$ in length at the rate of $2 \times 10^{-3} \text{ m}^3/\text{s}$. The pressure required to maintain the flow is (Viscosity of water $= 10^{-3} \text{ SI units}$):