Electrical energy supplies power to various types of appliances such as lights, fans, refrigerators, televisions, computers, motors etc. The amount of electrical energy consumed per second by an electrical device can be easily calculated from VI. Every house has an electricity meter, which measures the voltage (V) and how much electricity (I) is flowing, from which it can be known how much electrical power (P=VI) is being supplied to a house every second. By multiplying the total time with this, the electrical energy used can be found. The conventional unit of electricity cost is the kilowatt-hour or unit I the electricity bill we pay is calculated in this unit.
Types of electricity meters:
1.Analog Meters: The meters where the electricity bill is calculated by the rotation of the wheel are called analog kilowatt hour meters.
2. Digital Meters: The meters which calculate the electricity bill using number system are called digital kilowatt hour meters.
How to calculate electricity bill:
We know that there are two methods of calculating household electricity bills. One of them is the analog meter method and the other is the digital meter method l In the analog meter method- the inner wheel of the meter turns 1 unit every 10 times, thus increasing. On the other hand, in the digital system, the bill amount or unit can be seen directly on the meter display.
Arithmetic calculation of electric meter bill:
Mathematical solution:1
How much electricity will be consumed if a 60 watt bulb is lit for 5 hours per day for 30 days? If the price per unit is 5 taka then what is the total cost for this amount of electricity?
Given, P= VI = 60 W, t = 5 X 30 hours
Energy consumed, E = P t/ 1000 KWH
= 60X 5X30 / 1000 Units = 9 units
Total electricity consumption cost =9 X5 = 45 taka (when per unit price as 5 taka)
Mathematical solution no-2
In a dormitory in 40 rooms, 40 lamps of 20 W are lit for 6 hours a day, and 40 ceiling fans of 70 W are turned on for 12 hours. A 100 watt TV in the common room runs for 6 hours daily. Find the electricity bill for the month of March 2024 if the hostel has 220 volt supply. (Price per unit 5 Taka).
Solution:
A. Energy consumed for a 20 watt lamp,
=20 X40 X6 /1000 kilowatt-hours
= 4.8 kilowatt-hours or units
B. Energy consumption for a 70 watt fan,
=70 X40 X12/1000 kilowatt-hours
=33.6 kilowatt-hours or units
C. Energy consumed for a 100 watt TV,
=100 X1 X6/1000 kilowatt-hours
=0.6 kWh
Total energy consumed for 31 days of March 2024
= (4.8+33.6+0.6) units
=39 units X31= 1209 units (march month is 31 days)
Electricity bill for the month of March 2024-
= 1209 units X5 = 6045 Taka