Question

Two bulbs of 40W each are lighted for eight hours daily. Find the cost of electrical energy consumed by then in one week at re.3 per unit.

Answer 1

So we have,

power of one bulb = 40 W

time = 8 hrs

Amount of electrical energy consumed in one day by the two bulbs,

= 40 × 8 × 2 / 1000

= 0.64 kWh

Amount of electrical energy consumed in one week, i.e., 7 days,

= 0.64 × 7 = 4.48 kWh

Now, the total cost of electrical energy is,

3 × 4.48 = ₹ 13.44

Answer 2

Dear Student,

● Answer -

Cost of electrical energy = 13.44 Rs

◆ Explaination -

Total time for lighting the bulbs is -

Time = 8 hrs daily × 7 days

Time = 56 hrs

Electrical energy consumed by one bulb in this time is -

Energy consumed = Power × Time

Energy consumed = 40 × 56

Energy consumed = 2240 Wh

Energy consumed = 2.240 kWh

Energy consumed = 2.240 units

Cost of energy consumed by 2 such bulbs is -

Cost of energy = 2 × 2.240 × 3

Cost of energy = 13.44 Rs

Therefore, cost of electrical energy consumed is 13.44 Rs.

Thanks dear. Hope this helps you...