WHAT IS 'POWER' & 'ENERGY '?
Most of us usually confuse, very often, between ‘power’ & ‘energy’. The rate of doing work by the electricity per second (or per hour) is called Power.
Unit of power is “Watt”.
1 Watt = 1 Joule per second.
‘Watt’ (W) is a very small unit fence we use ‘Kilo Watt’ (KW) as a unit of commercial level.
Again, Power (P) = Voltage (V) X Current (I) in Watt.
= VI Watt = (IR) X (I) Watt = I2R Watt.
Then, what is ‘energy’?
The capacity or ability of doing work is called “energy”.
The quantity of work is done in a given period of time is called ‘energy’. It is the product of ‘power’ & ‘utilized time period’. The unit of energy is Watt-hour.
1 watt hour= Quantity of work done by one watt of power in one hour.
Again, this ‘watt-hour’ is a small unit. We normally use ‘KW-hour’ in commercial level.
Let us take an example to distinguish between ‘power & energy’:
A residential house has the following electrical points:
- Bulbs= 6nos of 100 watt each used for 8 Hours.
- Heater=1 no. of 1000 watt used for 2 Hours.
- Fan =2 nos. of 80 watt each used for 6 Hours.
What is the “power” & “energy” in this house?
To know the “power”, we have to add the wattage as follows:
Bulbs = 100 x 6 = 600 watts
Heater= 1000 x 1 = 1000 watts
Fan= 80 x 2= 160 watts
Total wattage = 1760 watts.
Hence the used “power” in that house is 1760 watts or 1.76 KW.
To know the ‘energy’ utilized, we have to multiply the utilized hours of each appliance & find out the sum total.
Bulb: 100 watt X 6 X 8 hour= 4800 watt hour
Heater: 1000 watt X 1 X 2 hour= 2000 watt hour.
Fan: 80 watt X2 X 6 hour = 960 watt hour
Total energy used per day =7760 watt hour = 7.76 Kilo Watt Hours
7.76 Kwh = 7.76 Units ( 1 Kwh = 1 Unit)
Energy for a month =7.76 x 30=232.80 units.