Question

5 bulbs of 50 W each, operate for 5 hours per day. If the cost of the energy consumed in 30 days is ₹ 375, find the cost of one unit of electricity.

• A.
  ₹ 7
• B.
  ₹ 10
• C.
  ₹ 12
• D.
  ₹ 8

Answer 1

The correct option is B

₹ 10
Given,
Power rating of the bulb = 50 W
Electrical energy consumed by 1 bulb in a day = Power rating of the bulb x Operating time of the bulb in a day
= 50 W x 5 hours
= 250 Wh
Energy consumed by 5 bulbs in a day = 250 Wh x 5 = 1250 Wh
Energy consumed by 5 bulbs in 30 days = 1250 Wh x 30 = 37500 Wh

We know that
1 kWh = 1000 Wh Or 1 Wh = 0.001 kWh
=> 37500 Wh = 37500 x 0.001 = 37.5 kWh

Since 1 kWh = 1 unit of electricity
=> 37.5 kWh = 37.5 units
Given, the cost of 37.5 units of electricity = ₹ 375
Cost of 1 unit of electricity = 375/37.5
= ₹ 10

Thus, the cost of 1 unit of electricity is ₹ 10.