What is the current through an ideal $P-N$ junction diode shown in the figure below? (in $mA$)

When radiation of the wavelength $\lambda$ is incident on a metallic surface,the stopping potential is $4.8 \ V$. If the same surface is illuminated with radiation of double the wavelength,then the stopping potential becomes $1.6 \ V$. Then,the threshold wavelength for the surface is:

The angle between the curves $y^2=4x+4$ and $y^2=36(9-x)$ is (in $^{\circ}$)

The cubic equation whose roots are thrice to each of the roots of $x^3+2 x^2-4 x+1=0$ is

If an electric heater is rated at $1000\, W$,then the time required to heat one litre of water from $20\, ^oC$ to $60\, ^oC$ is