Two capacitors $C_1$ and $C_2$ are charged to $120\, V$ and $200\, V$ respectively. It is found that by connecting them together,the potential on each one can be made zero. Then:

The number of circles that touch all the straight lines $x+y=4$,$x-y=-2$,and $y=2$ is

Which of the following series is $NOT$ included in the sub-class $Thalamiflorae$?

What are plasmodesmata?

Electrons ejected from the surface of a metal,when light of certain frequency is incident on it,are stopped fully by a retarding potential of $3 \ V$. Photoelectric effect in this metallic surface begins at a frequency $6 \times 10^{14} \ s^{-1}$. The frequency of the incident light in $s^{-1}$ is : [Planck's constant $= 6.4 \times 10^{-34} \ J \ s$,charge on the electron $= 1.6 \times 10^{-19} \ C$]

The work function of nickel is $5 \text{ eV}$. When light of wavelength $2000 \text{ \AA}$ falls on it, it emits photoelectrons. The potential difference necessary to stop the fastest electrons emitted is (given $h = 6.67 \times 10^{-34} \text{ J-s}$): (in $\text{ V}$)