If the length of the filament of a heater is reduced by $10\%$,the power of the heater will

$A$ room heater is rated $400 \text{ W}$, $220 \text{ V}$. If the supply voltage drops to $200 \text{ V}$, what will be the power consumed (approximately) (in $\text{ W}$)?

$A$ Watt-hour meter measures:

Two bulbs have resistances in the ratio $1 : 2$. They are connected in parallel to a constant voltage source. What is the ratio of power dissipated in them?

$A$ uniform heating wire of resistance $36 \, \Omega$ is connected across a potential difference of $240 \, V$. The wire is then cut into half and a potential difference of $240 \, V$ is applied across each half separately. The ratio of power dissipation in the first case to the total power dissipation in the second case would be $1:x$,where $x$ is........... .

An electric kettle draws $4\, A$ current at $220\, V.$ How much time (in minutes) will it take to boil $1\, kg$ of water starting from a temperature of $20\, ^oC$? (Assume the boiling point of water is $100\, ^oC$ and specific heat capacity of water is $4.2\, J/g\, ^oC$)