Arrange the following in order of increasing dipole moment : $H_2O$,$H_2S$,$BF_3$.

$A$ uniform magnetic field $B$ that is perpendicular to the plane of the page passes through the loops,as shown. The field is confined to a region of radius $a$,where $a < b$,and is changing at a constant rate. The induced emf in the wire loop of radius $b$ is $\varepsilon$. What is the induced emf in the wire loop of radius $2b$?

The work done in increasing the size of a rectangular soap film from $10 \, cm \times 6 \, cm$ to $10 \, cm \times 11 \, cm$ is $3 \times 10^{-4} \, J$. The surface tension of the film is:

$A$ segment of wire vibrates with a fundamental frequency of $450 ~Hz$ under a tension of $9 ~kg-wt$. The tension at which the fundamental frequency of the same wire becomes $900 ~Hz$ is

$A$ household refrigerator with a coefficient of performance $1.2$ removes heat from the refrigerated space at the rate of $60 \ kJ/min$. What would be the cost of running this fridge for one month ($30$ days)? (Assume it is used for $4$ hours each day and the cost of one electrical unit is $6 \ Rs$.)

$A$ transistor having a $\beta$ equal to $80$ has a change in base current of $250 \mu A$. The change in collector current is: