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Power has magnitude, but no direction and hence is known to be a scalar quantity. A system’s average power is directly proportional to the work done by the energy used and is inversely proportional to the time consumed to complete the work. As per average power definition, it is the total quantity of work done over a specific period.
The average amount of energy utilised or work done per unit of time is known as average power. In specific cases, the average power is represented as power only. For example, when the work done over time increases, the average power also increases. However, if there is no change in the quantity of work done over a continuously increasing time, the average power decreases.
Thus, work that can be finished within a short-term duration demands higher average power, and the work done for an extended period has comparatively less average power requirement. You can read about it in a detailed average power definition.
The SI Unit of average power is Watt and is represented as ‘w’ where Watt is Joules per second.
Average Power Formula
From average power definition, it is clear that average power is the proportion of total work done & the total time taken.
Therefore,
Average Power = Total Work Done/Total Time Taken
P=ΔW/ΔT
where,
P = Average Power
ΔW = The total quantity of energy consumed or the total quantity of work done.
ΔT = The total quantity of time taken.
The above equation of the average power formula gives the system’s average power value.
Average power varies with the gross energy consumed & the gross work done. Average power is directly proportional to the gross work done, whereas inversely proportional to the time taken.
For an electrical circuit, the average power is the product of the electric current passing throughout the circuit and the circuit’s supply voltage.
According to the electric circuit’s Ohm’s law, the average electric power is the product of the square of electric current passing throughout the circuit and the resistance of the circuit. It varies directly with varying voltage and varying current at constant circuit resistance.
P = VI or P=I²R
Where
P = average Power
V = voltage applied across the circuit.
I = electric current flowing throughout the circuit.
R= Resistance
Average Power Measurement
Average power is the quantity of work carried out over a specific period. The dimensional formula of average power is L²MT-³.
In the SI units, Watt measures average power. Therefore, the symbol for Watt is ‘W’.
According to the International Systems Unit, for a total time of one second, if the total quantity of work done or the energy consumed is one joule, the average power is one Watt.
Various other units used to measure average power are as follows:
- Horsepower
- Foot pounds per minute
- Ergs per second
- BTU per hour
- dBm
- Tons of refrigeration
- Calorie per hour (Cal/h)
The above units of measuring average power are area-specific. Different countries use different units for measuring the rate of work done. However, the International System’s Average Power-Watt unit is accepted worldwide. It is a standard measuring unit of power.
Watt is used in honour of James Watt (1736-1819), a Scottish mechanical engineer. In 1770, he invented improved steam engines and explained the concept of power. He introduced power as the new way of comparing his engines to what they would replace – horses.
Today, motor vehicles’ or machinery Power is often measured in terms of Horsepower (hp).
According to the British Imperial System, one Horsepower is the power required to lift a mass of 33,000 pounds on one foot in one minute. Thus, one hp equals 33,000 foot-pounds of work in a minute.
In the International System of Unit, the electrical equivalent of 1 hp is 746 watts. The heat equivalent of 1 hp is 2,545 BTU per hour.
Metric Horsepower is another unit of Power. It is equal to 0.9863 hp.
Average Power is measured using a Wattmeter.
Difference Between Power and Average Power
According to average power definition, it is the proportion of total work done to the gross time taken. However, Power is the rate of doing work at a particular time. Thus, we can obtain average power from the average quantity of work done at varied time intervals. Therefore, all instantaneous power values are first added and then divided by the total time interval.
Conclusion
Average power definition states the ratio of total work done and total time taken. It is denoted by P. The SI unit of measurement for average power is Watt. The device used to measure average power is a wattmeter. Average power formula is P=ΔW/ΔT, and P = VI for electric circuits. There is no difference between power and average power. Thus, average power is commonly known as power only.
