Define one watt.
Find the resistance of bulb rated as $100\, W -250 \,V$.
$1\, kW h =3.6 \times 10^{6}$ joule.
When two resistors of resistances $R_{1}$ and $R_{2}$ are connected in parallel, the net resistance is $3\, \Omega$. When connected in series, its value is $16\, \Omega$. Calculate the values of $R_{1}$ and $R_{2}$
How many joule are there in one kilowatt hour ?