Derive an expressions for electric power in terms of current and resistance.

Derive an expressions for electric power in terms of resistance and potential difference.

An electric lamp of $200\mathrm{\Omega }$ and a toaster of $100\mathrm{\Omega }$ are connected in parallel to $220 \mathrm{V}$ electricity source. An electric iron is connected to the same source permits the same current as the total flowing through both appliances. What is the current passing through the electric iron?

An electric lamp of $200\mathrm{\Omega }$ and a toaster of $100\mathrm{\Omega }$ are connected in parallel to $220 \mathrm{V}$ electricity source. An electric iron is connected to the same source permits the same current as the total flowing through both appliances. Calculate the power of electric iron.