If a set $A$ has $n$ elements,then the total number of subsets of $A$ is:

$A$ $U$-tube has a left limb with a cross-sectional area that is one-quarter of the right limb. The tube contains mercury (density $13.6 \ g/cm^3$). The level of mercury in the narrow left limb is at a distance of $36 \ cm$ from the upper end of the tube. What will be the rise in the level of mercury in the right limb if the left limb is filled to the top with water (in $cm$)? (Density of water = $1 \ g/cm^3$)

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

If the angles of a triangle are in the ratio $4:1:1$,then the ratio of the longest side to the perimeter is

The point of intersection of the lines $l_1: r(t)=(i-6j+2k)+t(i+2j+k)$ and $l_2: R(u)=(4j+k)+u(2i+j+2k)$ is

When $n-p-n$ transistor is used as an amplifier: