Work, Energy, and Power – Definition, Types, Examples

Work, Energy, and Power are important physics concepts. They are part of the basic physics module and are important to build an understanding of the subject.

All three concepts are correlated and have common elements and an impact on each other. Especially work and energy are working side by side almost all the time. This is mainly due to energy’s presence for doing work.

In this article, we will look at basic physics concepts like Force, Displacement, Forms of energy, the law of energy conservation, and many other important physics concepts.

They all are relevant for an exam. Some elements that we’ll see in the article below are – definition, formula, derivation, application, and much more.

Work

Gaspard-Gustave Coriolis was the mathematician behind the discovery of concept work. Work is a situation when there is a displacement of an object from point A to point B by an applied force.

The magnitude of the force applied divided by the distance moved in the force direction gives us work done by force. Work looks at the idea of the magnitude, not direction. The SI unit of work is Joule or J and denotes it in all the formulas.

Work done = Force x Displacement or W = F x s

Factors Affecting Work

1. Force

Force is a physical pull or push that leads to a change in an object’s velocity and acceleration. It is a vector quantity and focuses on direction and magnitude both. In the case of zero force on an object, the work done becomes zero.

2. Displacement

Displacement refers to the shortest distance covered by an object from start to end position. If the displacement is zero in a direction, force acting becomes zero, and thus work done is zero as well.

3. The Angle between the Force Vector and the Displacement Vector

The work done by the force on an object is of three types – positive, negative, and zero. This depends on the displacement direction of an object. When an object moves opposite to the force direction like friction by an object moving forward, the work done is negative by friction.

When displacement is perpendicular to the force direction, work done is zero as the force applied is zero. And when the object moves in the same direction as force direction, the work done is positive.

4. Work Done Against Gravity

The work done against gravity is equal to the lifting height of the object and the product of the weight. The formula for work done against the gravity is –

W = m x g x h ( W – work done, m – object mass, g – gravity acceleration, and h – height of object lift )

Energy

The energy converts to form but it’s not created or destroyed.

An example is the production of electric energy from solar energy. In the case of work done, object working loses energy while work done on an object gains energy.

And the object with energy can exert force on another object to transfer energy. Thus the work done capacity measures the energy.

The SI unit of energy is joule or J which is the same as work done.

Forms of Energy

There are various forms of energy.

1. Chemical Energy

When any chemical substance goes under transformation by a chemical reaction and transforms another chemical substance, there is the production of chemical energy. The bonding and diffusing of chemical bonds of different elements is an example of this.

A chemical reaction has the capability to transform any chemical substance into any form of energy. Photosynthesis is a classic example of a chemical reaction in which solar energy converts to chemical energy.

2. Electrical Energy

When kinetic energy produces energy, it becomes electrical energy. Electromechanical generators are responsible for generating electricity at power stations. These generators use heat engines to function. These heat engines run on the kinetic energy of water and wind.

Sometimes chemical combustion or nuclear fission can also help heat engines to function.

3. Light Energy

The electromagnetic radiation produces light as a form. It is a type of kinetic energy that helps us see things around us. Objects like bulb, light, and the sun release some electromagnetic radiation that produces light energy or light.

Space transfers light energy in a natural way like solar energy.

4. Heat Energy

The kinetic energy around the object produces heat energy. A daily life example is hot water cools down in some time as there is heat loss as the temperature in the surrounding is lower.

The molecules show a random motion that makes them bounce off each other and thus end up transferring heat. The energy in transit is another name for this. This is because the heat travels from high temperature to lower temperature.

5. Nuclear Energy

The nucleus of atoms possesses nuclear energy which is one of the most dangerous weapons. The nuclear bombing in japan during world war II caused enormous destruction in the country. The fusion or fission reaction leads to the release of nuclear energy from the nucleus.

The reaction of this fusion is vast and thus controlling it will enable energy production. This is the process which nuclear weapon production uses as well.

6. Kinetic Energy

Any energy that is in motion becomes kinetic energy. There is a presence of energy in the object because there is motion. The direction and dimension have no impact on kinetic energy.

Running water, moving cycles all are examples of this energy. The mass and velocity are two important elements that decide kinetic energy. The formula for kinetic energy is –
Kinetic Energy = 12m × v2

7. Potential Energy

The work done decides the potential energy as this is the energy that the object has stored. An example is a notebook on a table or a pen in a pen holder. Mass of the object, height, and gravity acceleration are three important elements here.
Potential Energy = m × g × h

Mechanical Energy

Mechanical energy is of an object in motion or at rest. It is basically the energy that an object has when there is work done on it. It possesses the energy due to motion or position. Mechanical Energy = ( Kinetic + Potential ) Energy
OR Mechanical Energy = 12m x v2 +m x g x h

Different Types of Energy Resources

The most common use of energy sources is fuel. And fuels are required for the functioning of machineries, automobiles, and industries. This is mainly to generate electricity and they are of two types – Non-renewable and Renewable.

Non-renewable Resources of Energy
The resources that don’t have the ability to be renewed after use are non-renewable resources. They are mostly fossil fuels like oil, natural gas, and coal.

Renewable Resources of Energy
These resources have the ability to regenerate after one use and are available for continuous consumption. They are wind, water, and solar energy.

Types of Energy according to their Resource

Einstein’s Equivalence of Mass and Energy

Einstein’s theory of relationship equivalence of mass and energy is very important in this topic.

According to this equation, the body energy is equal to the mass of the body multiplied by the square of light speed.

The famous equation is E = mc2. The E is for energy, m is for mass and c is the light speed in a vacuum ie 3 x 108 m/sec.

Law of Conservation of Energy

The concept of energy stands on the law of conservation of energy. It says that energy only transforms from one type to another and is not capable of creating and destroying.

And also the energy remains the same and the transformation process has no impact on the quantity. This condition stays valid in all transformations, locations, and conditions.

Energy Conservation

The idea of energy conservation is very important looking at the current situation. And it is definitely not about limited resource use but good resource management.

There should be a reduction in limited supply-demand and efficiency in resource management. The idea is to opt for alternatives for these resources.

Law of Conservation of Energy Examples

• The conversion of chemical energy from the battery to electrical energy in the torch leads to heat and light energy.
• The dams use this where the potential energy of water converts to the turbine’s kinetic energy and eventually electric energy.
• The loudspeaker uses electric energy that converts to sound energy. And the conversion is vice versa in the microphone.
• The burning of fuel converts chemical energy to heat and light energy.
• The human body uses the conversion of food’s chemical energy to thermal energy to keep itself warm.

Work-Energy Theorem

The work-energy theorem states that “work done by all forces is equal to change in kinetic energy.

The formula for this theorem is – Kf – Ki = W (Final Kinetic Energy – Initial Kinetic Energy = net work done).

This includes work by all forces no matter what it was like friction or normal force. It will be valid to say that w1 + w2+ w3 = kf – ki. In this w1 is the normal force, w2 is friction and w3 is work by gravity.

Principle of Work and Energy

The work-energy principle is related to work and kinetic energy. It states that the net work done on the object is equal to kinetic energy’s change in the object. And it is vice versa in case of reducing kinetic energy.

This principle comes from the concept of law conservation of energy.

Work vs Energy

Power

It is a physical concept and has several definitions that change according to contexts. Here in the context of work and energy, power is simply the rate of doing work.

The energy that the object consumes on average working per unit time is average power. The power is directionless and thus a scalar quantity. The SI unit of power is joules/second or Watt. Watt is the power required to one joule of work in a second.

James Watt was the developer of steam engines. The formula for power is –
P = W/ T (P – Power, W – Work done, and T – Time taken)

Horse Power

Power uses another unit that is horsepower which is equal to 746 Watt. or we can I horsepower = 0.75 KW.
1W x 1 s = 1 Watt Second
3600 joule = 1 Watt Hour
3.6 x 106 Joule = 1 KiloWatt Hour

Electric Power

Power is closely related to the concept of electrical energy that we saw above. Electric power is the rate of doing work or transforming energy in an electric circuit. It measures the energy required in a particular time frame.

The physics definition of electric power is the transfer rate of electrical energy by the circuit per unit time. Mostly potential energy is the initial energy inside the circuit. P denotes the Electrical power and Watt measures it.

The formula is –
P = VI ( V – volts and I – electric current )

Important Points About Power

• The rate of using energy for any purpose is termed as power
• It decides the work quickness
• It is capable of changing ad there are two methods to measure –

1. Instantaneous – The power at a particular time point
2. Average – The total energy / total time ( average of instantaneous power )

Conclusion

We saw some of the important basic physics concepts for UPSC above. Some highlights of the article were the law of energy conservation, types of energy, Work vs energy and much more.

There are high chances of this topic appearing in the General Science Prelims paper and maybe in physics optional paper as well. This is because it comes under 7th – 9th physics and which is crucial for prelims paper mainly.

Other competitive exams like SSC, RRB, and Banking may be interested in this topic too. All the candidates of the competitive exam must refer to this article for better preparation and understanding.