Question

Calculate the monthly bill for a heater of resistance 40Ω, which is used on 220V mains, such that its daily use is for 5 hours. The cost of electric energy is Rs 3.60per kWh.

Answer 1

Answer:

Resistance of heater = 20Ω

V = 240v

Time for which is the heater used daily = 2 hrs

Cost = Rs. 4.30 per kWh

Total Work done by the heater every day =

\frac{ {v}^{2}}{r} \times t = \frac{ {240}^{2} }{20} \times 2 = \frac{240 \times 240}{20} \times 2 = 2880 \times 2 = 5760

r

v

2

×t=

20

240

2

×2=

20

240×240

×2=2880×2=5760

Total work done by the heater in a Month of 30 days = 5760*30/1000

=>172.8kWh

Total Cost = 172.8 * 4.30 = Rs. 743.04