calculate the monthly bill for heater of resistance 40 ohm which is used on 220V mains such that its daily use is for 5 hrs. the cost of electric energy is Rs.3.60 per kwh.
As P= V2/R = 220 x 220 /40 = 1210 W
The total energy consumed in 30 days would be
= 1210 W ×5.0 hour/day ×30 days
= 181500W h
= 181.5 kW h
Thus the cost of energy for 30 days is
181.5 kW h×Rs 3.60 per kW h = Rs 653.40