An electric refrigerator rated 400 W operates 8 hours/day. What is the cost of the energy to operate it for 30 days at ₹3.00 per kW h?

Correct option is C

Correct Answer: (C) ₹288

Explanation:

The cost of electricity is calculated using the formula:

$Power\times Time\text{Energy Consumed}=\text{Power}\times \text{Time}TotalCost=EnergyConsumed\times Costperunit\text{Total Cost}=\text{Energy Consumed}\times \text{Cost per unit}$

Step 1: Calculate daily energy consumption

• Power rating of the refrigerator = 400 W = 0.4 kW
• Time of operation per day = 8 hours

$=0.4\times 8=3.2kWh\text{Energy per day}=0.4\times 8=3.2\text{ kWh}$

Step 2: Calculate total energy for 30 days

$96kWh\text{Total Energy}=3.2\times 30=96\text{ kWh}$

Step 3: Calculate total cost

• Given cost per kWh = ₹3.00

$₹288\text{Total Cost}=96\times 3=₹288$

Key Points:

• 1 kWh = 1 unit of electricity.
• The power rating (W) should be converted into kW (divide by 1000) before calculations.
• The cost calculation is based on multiplying total energy (in kWh) by the cost per unit.