If three resistors of resistance $2 \,\Omega$,$4 \,\Omega$ and $5 \,\Omega$ are connected in parallel,then the total resistance of the combination will be:

$10$ resistors,each of resistance $10\,\Omega$,can be connected to obtain maximum and minimum equivalent resistance. The ratio of maximum to minimum equivalent resistance will be $..........$.

Find the equivalent resistance between points $A$ and $B$.

$A$ heater $A$ gives out $300 \ W$ of heat when connected to a $200 \ V$ $d.c.$ supply. $A$ second heater $B$ gives out $600 \ W$ when connected to a $200 \ V$ $d.c.$ supply. If a series combination of the two heaters is connected to a $200 \ V$ $d.c.$ supply,the heat output will be ................. $W$.

$A$ wire of resistance $R$ is bent to form a circular ring. Find the equivalent resistance between two points $X$ and $Y$ on its circumference. (The angle $XOY = \alpha$ is given.)

Three unequal resistors in parallel are equivalent to a resistance of $1 \ \Omega$. If two of them are in the ratio $1:2$ and if no resistance value is fractional,then the largest of the three resistances in ohms is