If $u+iv = \frac{3i}{x+iy+2}$,then $y=$

Two opposite and equal charges $4 \times 10^{-8} \, C$ are placed $2 \times 10^{-2} \, cm$ apart,forming a dipole. If this dipole is placed in an external electric field of $4 \times 10^8 \, N/C$,what are the values of the maximum torque and the work done in rotating it through $180^o$?

$A$ parallel plate capacitor with oil (dielectric constant $K = 2$) between the plates has capacitance $C$. If the oil is removed,the capacitance of the capacitor becomes:

Two masses of $10\,kg$ and $20\,kg$ respectively are connected by a massless spring as shown in the figure. $A$ force of $200\,N$ acts on the $20\,kg$ mass. At the instant when the $10\,kg$ mass has an acceleration of $12\,m/s^2$ towards the right,the acceleration of the $20\,kg$ mass is: (in $,m/s^2$)

How many moles of $KMnO_4$ are required to oxidize $1 \ mol$ of $FeC_2O_4$ in an acidic medium?

Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities of maxima and minima is