An electric bulb draws a current of 0.8a from 250 v mains. the bulb is used on an average 8
hours a day, if energy costs rs 3 per kwh, calculate the monthly bill for 30 days.

First, we must find the power consumed by the light bulb. This is given by:
Power = voltage * current
Power = 250 * 0.8
Power = 200 W = 0.2 kW

Now, we must calculate the number of hours that the bulb is used, as the price given to us is in Rs/kWh. This is:
8 hours per day * 30 days
= 240 hours

Total kWh = 0.2 * 240
Total kWh = 48 kWh

Bill = 3 * 48
Bill = 144 Rs