A Brief Note on Important Points about Power

In physics, power is a physical quantity related to work and energy. It is the rate at which energy is used. If a person does a different type of work, then the power required will also differ. When you push or pull an object by applying a force, there is some displacement seen. This is known as work. In contrast, energy is the capacity to perform a task. Lastly, power is the time rate of work done or energy transferred. 

Let’s discuss these fundamentals of physics with the main focus on power.

A full explanation of power

Among the three fundamentals of physics,  power is referred to as the rate at which the work done is divided by the time interval t, or it can be written as W/t. Power is something that we encounter in our day-to-day lives very often. We can call it the amount of energy expended or absorbed per unit time. Power is a scalar quantity with a magnitude but no direction. 

In the field of science, this scalar quantity is a product of the force applied to an object and the speed of the object that is moving in a particular direction as a result of force. It is the rate at which energy is used. Additionally, the power of a motor is expressible as a product of torque and angular velocity of the output shaft of the motor. 

To understand the basic concept of power, let’s see two examples. If a powerful car is accelerating at a good speed, it will perform a large amount of work by exhausting a large amount of fuel in a minimum time. 

Another example we can consider is a person pushing a box that weighs 30 kg to a 10 m distance. Another person is assigned the same task. Suppose the first man finishes his work in 1 minute, while the second one takes 3 minutes to complete. This means there is a relationship between power and work done. Of course, the first man will have more power than the second man because he completes in the minimum time interval. It decides how quickly work could be done.

Average power 

Average Power can be considered as a ratio of work done by the body when the time of duration is taken as t. In simple terms, it is the average amount of work done per unit time. 

Pav = W/t

Instantaneous power 

Instantaneous power is the power at any given moment of time and the limiting value of the average power when the time interval touches zero.

We know that P = dW/dt.

It is interesting to know that when we talk about electrical circuits, the power in an AC circuit is defined as a product of instantaneous voltage and the instantaneous current flowing through that circuit. 

We can also write it as p = v × i

Where p represents the instantaneous power in watts

v represents the instantaneous voltage in volts

i represents the instantaneous current in amperes.

Formula of power 

The formula of power is expressed in terms of various physical quantities, including force, work, time, current, voltage etc. Here, we will discuss these formulas. Take a look. 

P = W / t 

In this formula, P is the power, W is the work done, and t is the duration taken by an object to perform work. 

P = F. dx / dt

In this formula, F is the magnitude of the force that is applied to move an object in a particular direction. dx is the distance travelled by the object per unit of time. 

P = F.v 

In this formula, F is the magnitude of the force that is applied to move an object in a particular direction, and v is the speed of the object on which F force is applied. 

Unit of power 

In the International System of Units or SI unit, the power of an object is measured in watts or Newton metres per second. 

SI unit of power 

Watt(W)

1 hp = 746 W

1 KW = 1000 W

1 MW = 106 W 

1 GW = 109 W

Conclusion

This article shared insights on some important points about power, a scalar quantity. An important concept to note here is that it is the rate at which energy is used per unit of time. Additionally, it decides how quickly work could be done. All the formulas included in this article are valid for all types of general situations. It is possible to now know the power of any type of system by using the above formulas. Interestingly, power can be called the derivative of work.