A fluorescent lamp of $20 W$ and an incandescent bulb of $150 W$ are used for $5$ hours per day in the month of February $2008$ . If the cost of one unit of electrical energy is $₹ 1.5$ , which of the two is more economical to use and by how much?

Open in App

Solution

Step 1: Given data
Power $P_{1} = 20 W$ for lamp and
$P_{2} = 150 W$ for the bulb
Clearly, the bulb uses more power and is not economical.
Step 2: Calculating the cost
Units of electrical energy consumed by the lamp $= P_{1} \times h o u r s u s e d$
$= 20 \times 5 = 100 W h = 0.1 k W h$
Therefore, cost $= 1.5 \times 0.1$
$= ₹ 0.15 / d a y$
Units of electrical energy consumed by the bulb $= P_{2} \times h o u r s u s e d$
$= 150 \times 5 = 750 W h = 0.75 k W h$
Therefore, cost $= 1.5 \times 0.75$
$= ₹ 1.125 / d a y$
Step 3: Finding which one is more economical to use and by how much
The total no. of days in February $2008$ is $29$
The cost of electrical energy consumed by the lamp is $₹ 0.15 / d a y$
The cost of electrical energy consumed by the lamp in February $= 29 \times 0.15$
$= ₹ 4.35$
The cost of electrical energy consumed by the bulb is $₹ 1.125 / d a y$
The cost of electrical energy consumed by the lamp in February $= 29 \times 1.25$
$= ₹ 32.625$
The lamp is more economical to use.
Difference in money $= ₹ (32.625 - 4.35)$
$= ₹ 28.275$
Hence, The lamp is more economical to use by $₹ 28.275$

Suggest Corrections

Similar questions

Five LED bulbs of 8 W each, two fans of 40 W each, electric motor 3kW and a geyser of 5 kW are used for 8 hours per day by a family. Calculate the total energy consumed in 30 days and the cost of electricity used in one day at the rate of Rs.5 per unit.

A bulb of 30 W is switched ON for 15 hours per day. How much electrical energy is consumed in the month of June?

How much money can be saved per month by using a compact fluorescent lamp of 15 W in place of an incandescent bulb of 100 W if they are used 8 hours per day for 30 days? (Take the cost of one unit of electrical energy as ₹2)

Seeta says that a compact fluorescent lamp uses less energy compared to an incandescent bulb. But Geeta, her friend, does not agree with this. Seeta proves it by calculating the money that can be saved per month by using a compact fluorescent lamp of $15 W$ in place of an incandescent lamp of $100 W$ if they are used $8 h o u r s$ per day for $30 d a y s$ . How did she prove it? (The cost of one unit of electrical energy is $2 r u p e e s$ )

in a household, an electric bulbs of 100 w is used for 10 hours and an electric heater of l000 w for 2 hours everday. calculate the cost of using the bulb and the heater of 30 days if the cost of one unit of electrical energy is two rupees.

Join BYJU'S Learning Program

A fluorescent lamp of 20W and an incandescent bulb of 150W are used for 5 hours per day in the month of February 2008. If the cost of one unit of electrical energy is₹1.5, which of the two is more economical to use and by how much?

A fluorescent lamp of $20 W$ and an incandescent bulb of $150 W$ are used for $5$ hours per day in the month of February $2008$ . If the cost of one unit of electrical energy is $₹ 1.5$ , which of the two is more economical to use and by how much?