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Power is a physical quantity in which energy transfers in a unit of time. It is a scalar quantity that has a magnitude but lacks direction. In physics, power is dependent on the amount of work done or energy transferred. It is also related to other quantities such as force, velocity, torque, angular velocity, current-voltage, etc.
One can measure power in watts according to the International System of units. This article will explore its meaning and the unit of power in electricity. Let us get into the depth of the topic.
What is Power?
Power, in general, is referred to as the amount of energy transferred or converted, divided by the time interval t.
In simpler terms, it is the rate of doing work per unit time. For example, when we burn coal, it releases energy more quickly than a few elements. It means that coal will deliver more power than these elements.
We can define power as a time-based quantity related to how fast we do work. The equation for power is as below:
Power = Work / Time
P= W / t
In this formula, W represents work done upon an object, and t is the time taken to perform that work.
One way to think about power is by taking an example of a bulb. 100 W bulbs have higher brightness than 20 W bulbs. Why?
The higher the power of a bulb, the more energy it releases compared to the bulb with 20 W power.
Let us see another example. Suppose there is a low-powered motor and a high-powered motor. Among the two, a low-powered motor will take longer to perform its work than a high-powered motor. As a result, we can say power is inversely proportional to the time taken for performing a task.
Different Units of Power in Electricity
Watt
According to the standards of measuring a quantity, we can measure power in watts. So, the SI unit of power is the watt, and we can write it as W. One watt can be defined as one joule of energy released per second.
Interestingly, the unit watt derives from the name of James Watt. He invented the condenser and coined this older unit of power in electricity known as horsepower.
So, 1 watt = 1 J/s
2. Other Units of Power in Electricity
Power measuring units also include:
- Foot-pounds per minute
- Ergs per second (erg/s)
- Food calories per hour or kilocalories per hour
- Decibel-milliwatts (dBm)
- BTU per hour (BTU/h)
- Horsepower (hp)
Conversions of Unit of Power in Electricity
Units | Equivalent Watt Unit |
1 Horsepower | 746 Watts (W) |
1 Centiwatt (cW) | 10-2 W |
1 Kilowatt (KW) | 1000 W |
1 Gigawatt (GW) | 109 W |
1 Megawatt (MW) | 106 W |
1 Terawatt (TW) | 1012 W |
1 Petawatt (PW) | 1015 W |
1 Exwatt (EW) | 1018 W |
1 Zettawatt (ZW) | 1021 W |
1 Yottawatt (YW) | 1024 W |
3.412142 British Thermal Unit per hour (BTU/hr) | 1 W |
0.737 Foot-Pounds | 1 W |
30 decibel-milliwatts (dBm) | 1 W |
0.24 calories per second (cal/sec) | 1 W |
Horsepower is an older unit of power in electricity that we usually use to measure the output of engines. The metric horsepower is equal to 735.5 watts.
On the other hand, a kilowatt is a standard unit for measuring electrical energy used by electrical appliances. Additionally, a megawatt is a unit of electricity we use in our daily lives. One megawatt is equal to 1000 kilowatts.
Conclusion
In this article, we saw the meaning of power in physics with its units. We can consider the units of power in electricity while calculating the power of mechanical systems and other systems.
It is a scalar quantity associated with torque and angular velocity. Though it depends on variables such as physical quantities, work and energy are the main focus while calculating power in physics.
This article must have helped build the basic concepts of power and its units, such as kilowatts and megawatts. You must have also learned about the applications of power in day to day life.
