An electric iron rated at 1200\,\text{W} is operated for 5\,\text{hours} each day for a pe… — JAMB UTME

An electric iron rated at $1200\,\text{W}$ is operated for $5\,\text{hours}$ each day for a period of $30\,\text{days}$ . If electrical energy costs $\text{₦}20.00$ per kilowatt-hour ( $\text{kWh}$ ), what is the total cost of electricity consumed by the iron over this period in Naira ( $\text{₦}$ )?

Answer: 3600 Naira

Answer

The total cost of electricity consumed by the iron over the 30-day period is 3600 Naira.

To find the cost of electrical energy in commercial units, express power in kilowatts (

1.2\,\text{kW}

) and time in total hours (

150\,\text{h}

). The energy consumed is

1.2 \times 150 = 180\,\text{kWh}

. At a tariff of

\text{₦}20.00

per

\text{kWh}

, the total cost is

180 \times 20 = 3600\,\text{Naira}

Step-by-Step Solution

Convert the power rating of the appliance from watts to kilowatts

P = \frac{1200\,\text{W}}{1000} = 1.2\,\text{kW}

Commercial energy consumption is calculated in kilowatt-hours (kWh), requiring power in kilowatts.

Calculate the total operating time in hours

t = 5\,\text{hours/day} \times 30\,\text{days} = 150\,\text{hours}

The usage duration across the month must be expressed in total hours.

Determine electrical energy consumed in kWh

E = P \times t = 1.2\,\text{kW} \times 150\,\text{h} = 180\,\text{kWh}

Energy is the product of power in kilowatts and time in hours.

Calculate total cost of energy consumed

\text{Total Cost} = 180\,\text{kWh} \times \text{₦}20.00/\text{kWh} = \text{₦}3600

Total cost is found by multiplying energy in kWh by the unit tariff rate.

Key Concept

Commercial electrical energy unit (kWh) and billing calculation

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