The equation of a curve in polar coordinates is $\frac{l}{r} = 2 \sin^2 \frac{\theta}{2}$. This equation represents:

An ideal heat engine operates on a Carnot cycle between $227\,^{\circ}C$ and $127\,^{\circ}C$. It absorbs $6 \times 10^4\, \text{cal}$ at the higher temperature. The amount of heat converted into work is equal to:

When a certain circuit consisting of a constant $e.m.f.$ $E$, an inductance $L$, and a resistance $R$ is closed, the current in it increases with time according to curve $1$. After one parameter $(E, L, \text{or } R)$ is changed, the increase in current follows curve $2$ when the circuit is closed a second time. Which parameter was changed and in what direction?

Which one feature is common to leech,cockroach,and scorpion?

The equation of the normal to the curve $y^4=ax^3$ at $(a, a)$ is

Which vegetable crop,released by $IARI$ New Delhi,is enriched with Vitamin $C$?