$A$ thermodynamic system undergoes a cyclic process $ABCDA$ as shown in the figure. The work done by the system in the cycle is

Curie temperature is the temperature above which

$A$ car $P$ approaching a crossing at a speed of $10\, m/s$ sounds a horn of frequency $700\, Hz$ when $40\, m$ in front of the crossing. The speed of sound in air is $340\, m/s$. Another car $Q$ is at rest on a road which is perpendicular to the road on which car $P$ is reaching the crossing (see figure). The driver of car $Q$ hears the sound of the horn of car $P$ when he is $30\, m$ in front of the crossing. The apparent frequency heard by the driver of car $Q$ is .... $Hz$.

Heating chloroform with aqueous sodium hydroxide solution forms

Who discovered viroids?

During the electrolytic reduction of alumina,the reaction at cathode is