Leaf blade is spinous in case of

$A$ coil of wire of radius $r$ has $600$ turns and a self-inductance of $108 \ mH$. The self-inductance of a coil with the same radius and $500$ turns is (in $mH$)

If the difference between the roots of $x^2+ax+b=0$ and $x^2+bx+a=0$ is the same,and $a \neq b$,then:

The major product of the following reaction is:

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile,$E^{+}$:
$(a)$ Chlorobenzene,$2,4-$dinitrochlorobenzene,$p-$nitrochlorobenzene
$(b)$ Toluene,$p-CH_3-C_6H_4-NO_2$,$p-O_2N-C_6H_4-NO_2$

Which one of the following elements reduces $NaOH$ to $Na$?