GuruIntroduction
In daily life, we usually to take electricity, the unseen force that drives our contemporary world for granted. Electrical power is essential for everything from lighting up our homes to powering industries. Its importance cannot be pointed out.Electrical energy is the energy linked to the motion of electric charges, used to operate different devices and systems daily. It can be produced from fossil fuels, nuclear power, renewable sources like solar and wind, and even chemical reactions in batteries.In this blog, we will take a closer look at the complexities in electric power and electrical energy and essential role that plays in forming our society.
The story of electrical power and energy
The story of electrical power began in the nineteenth century, when pioneers such as Michael Faraday and Nikola Tesla laid the groundwork for harnessing this natural phenomenon. Faraday's electromagnetism experiments, as well as Tesla's innovations in alternating current (AC) systems, paved the way for electricity's widespread utility adoption.Electric energy is primarily generated by the motion of electric charges. Benjamin Franklin and Alessandro Volta were early scientists who pioneered the study of this phenomenon in the 18th century, contributing to our modern electrified society.
Electric Power
The rate at which work is done in an electric circuit is called its electric power i.e.
Electric power = Work done in electric circuit / Time
When voltage is applied to a circuit, it causes current (i.e. electrons) to flow through it. Clearly, work is being done in moving the electrons in the circuit. This work done in moving the electrons in a unit time is called the electric power. Thus referring to the part AB of the circuit (See below Figure),
V = P.D. across AB in volts
I = Current in amperes
R = Resistance of AB in Ω
t = Time in sec. for which current flows
The total charge that flows in t seconds is Q = I × t coulombs and by definition
V = `frac WQ`
or
Work = VQ = VIt (∵ Q = It)
∴Electric power, P = `frac WT` = `frac{VIT}t` = VI joules/sec or watts
∴P = VI = `I^2`R = `frac{V^2}R` [∵V = IR and I = V/R ]
The above three formulae are equally valid for calculation of electric power in a d.c. circuit. Which one is to be used depends simply on which quantities are known or most easily determined.
Unit of electric power
The basic unit of electric power is joules/sec or watt. The power consumed in a circuit is 1 watt if a p.d. of 1 V causes 1 A current to flow through the circuit.
Power in watts = Voltage in volts × Current in amperes
The bigger units of electric power are kilowatts (kW) and megawatts (MW).
1 kW = 1000 watts ; 1 MW = `10^6` watts or `10^3`kW
Electrical Energy
The total work done in an electric circuit is called electrical energy i.e.
Electrical energy = Electrical power × Time
= V I t = `I^2`R t = `frac{V^2}R` t
The reader may note that formulae for electrical energy can be readily derived by multiplying the electric power by ‘t’, the time for which the current flows. The unit of electrical energy will depend upon the units of electric power and time.
1.If power is taken in watts and time in seconds, then the unit of electrical energy will be watt-sec. i.e.
Energy in watt-sec. = Power in watts × Time in sec.
2.If power is expressed in watts and time in hours, then unit of electrical energy will be watt-hour i.e.
Energy in watt-hours = Power in watts × Time in hours
3.If power is expressed in kilowatts and time in hours, then unit of electrical energy will be kilowatt-hour (kWh) i.e.
Energy in kWh = Power in kW × Time in hours
It may be pointed out here that in practice, electrical energy is measured in kilowatt-hours (kWh). Therefore, it is profitable to define it.
One kilowatt-hour (kWh) of electrical energy is expended in a circuit if 1 kW (1000 watts) of power is supplied for 1 hour.
The electricity bills are made on the basis of total electrical energy consumed by the consumer. The unit for charge of electricity is 1 kWh. One kWh is also called Board of Trade (B.O.T.) unit or simply unit. Thus when we say that a consumer has consumed 100 units of electricity, it means that electrical energy consumption is 100 kWh.
Use of Power and Energy Formulas
It has already been discussed that electric power as well as electrical energy consumed can be expressed by three formulas. While using these formulas, the following points may be kept in mind:
1.Electric power, P = `I^2`R = `frac{V^2}R` watts
2.Electrical energy consumed, W = `I^2`Rt = `frac{V^2}R` t joules
The above formulas apply only to resistors and to devices (e.g. electric bulb, heater, electric kettle etc) where all electrical energy consumed is converted into heat.
3.Electric power, P = VI watts, Electrical energy consumed, W = VIt joules
These formulas apply to any type of load including the one mentioned in point (i).
Conclusion
In summary, electricity and energy play a vital role in our modern electrical system, contributing to advancements in various fields. Knowledge of their fundamental principles offers a deeper understanding of electricity's impact on our world and aids in the transition to a more sustainable future. Through responsible utilization of electricity, we can fully realize its benefits for humanity.