The power factor of the circuit as shown in the figure is:

Who first suggested the idea of circular flow of genetic information?

Four point positive charges of same magnitude $Q$ are placed at four corners of a rigid square frame of side length $L$ as shown in the figure. The plane of the frame is perpendicular to the $Z$-axis. If a negative point charge $-q$ is placed at a distance $z$ away from the centre along the axis $(z << L)$, then:

Compound $X$ is the anhydride of sulphuric acid. The number of $\sigma$-bonds and the number of $\pi$-bonds present in $X$ are,respectively:

If $u=f(r)$,where $r^2=x^2+y^2$,then $\left(\frac{\partial^2 u}{\partial x^2}+\frac{\partial^2 u}{\partial y^2}\right)$ is equal to

$A$ man standing on a road has to hold his umbrella at $30^{\circ}$ with the vertical to keep the rain away. He throws the umbrella and starts running at $10 ~km/h$. He finds that raindrops are hitting his head vertically. The actual speed of raindrops is: