Unit of Energy

Unit of energy is a standard quantity used to measure the work done by a force or the amount of heat transferred. The SI unit of energy is the joule (J). Other Units of energy are electronvolt (eV), calorie, BTU, etc

In this article, we will define energy, discuss possible units to measure it, SI unit of energy, Conversion of energy unit, and some solved examples based on it.

Definition of Energy

Energy is the capacity to do work or generate heat.

Energy is a scalar quantity, i.e. it has magnitude but no direction. It exists in various forms and can be converted from one form to another, but the total amount of energy in a closed system remains constant, according to the law of conservation of energy.

Formula of Energy

If the force acting on the object is constant and in the direction of motion, then the work done by the force i.e Energy can be calculated using the formula:

W = F⋅d

where:

• F is the magnitude of the force,
• d is the displacement of the object in the direction of the force.

Unit of Energy

Energy is a fundamental concept in physics that represents the capacity of a system to do work or produce heat. Unit of Energy is a measure of the ability of a system or substance to do work or produce heat.

The unit of energy provides a standardized way to quantify and compare different forms of energy across various fields of science, engineering, and everyday life.

In the International System of Units (SI), the unit of energy is the joule (J). Other units of energy are ergs, BTU, Calorie, etc.

SI Unit of Energy

In the International System of Units (SI), joule is the universal unit of energy. It is versatile and applies to various energy forms.

The joule is integral to scientific, engineering, and practical applications because it provides a standard measure for energy transactions in physical processes.

Whether it is the energy consumed by electrical appliances, the calories burned during exercise, or the heat required to raise the temperature of a substance, the joule serves as a common denominator for quantifying energy.

What is 1 Joule?

One joule is defined as the amount of energy transferred when a force of one newton moves an object one meter in the direction of the force.

Unit of Energy in CGS System

The unit of energy in the CGS system is the erg (erg). In the SI system, the standard unit of energy is the Joule (J). The conversion factor between these units is 1 Joule = 10⁷ ergs.

Dimensional Formula of Energy

The dimensional formula of energy is [M¹L²T⁻²]

where:

• M represents mass
• L represents length
• T represents time

Unit of Energy List

The joule is the most widespread energy unit, but other units like the calorie, kilowatt-hour, and electronvolt are also used by scientists. These units are therefore a specific case of the type of units employed in the fields of nutrition, electricity, and atomic physics, respectively. Some common units of Energy are:

• Joule
• Calorie
• Kilojoule
• British Thermal Unit
• Kilocalorie
• Electronvolt
• Kilowatt-hour (kWh)
• Hartree
• Rydberg units

Conversion Between Unit of Energy

In the following table, conversion factors for different units of energy is given. These conversion factors can be multiplied to convert one unit to another unit.

From/To	Joule	Calorie	Kilojoule	British Thermal Unit	Kilocalorie	Electronvolt
Joule (J)	1	0.239006	0.001	0.000947817	0.000239006	6.242 × 1018
Calorie (cal)	4.184	1	0.004184	0.00396567	0.001	2.611 × 1019
Kilojoule (kJ)	1000	239.006	1	0.947817	0.239006	6.242 × 1021
British Thermal Unit (BTU)	1055.06	252.164	1.05506	1	0.252	6.585 × 1021
Kilocalorie (kcal	4184	1000	4.184	3.96567	1	2.611 × 1022
Electron volt (eV)	1.602 × 10-19	3.829 × 10-20	1.602 × 10-22	2.61144 × 10-22	3.829 × 10-23	1

By understanding these conversion factors, you can easily convert energy values from one unit to another for practical use.

Solved Examples on Unit of Energy

Example 1: Calculate the kinetic energy of a car traveling at a speed of 20 meters per second with a mass of 1000 kilograms.

Solution:

Given:

Mass = 1000 kg

Velocity = 20 m/s×

Kinetic Energy = 1/2mv²

= 1/2 × 1000 × (20)²

= 1/2 × 1000 × 400

= 2,00,000 joules

Example 2: Determine the potential energy of a book weighing 5 kilograms placed on a shelf 2 meters above the ground.

Solution:

Given

Mass = 5 kg

Height = 2 m

Acceleration due to gravity (g) = 9.8 m/s²

Potential Energy =mgh

= 5 × 9.8 × 2

= 98 joules

Example 3: Calculate the work done when a force of 50 newtons is applied to move a box a distance of 10 meters along the direction of the force.

Solution:

Force = 50 N

Distance = 10 m

Work Done = Force × Distance

= 50 × 10

= 500 joules

Frequently Asked Questions: FAQs on Unit of Energy

Why is the joule considered the standard unit of energy?

The joule is widely accepted and used in scientific research and common applications due to its simplicity and practicality.

How does energy affect the environment?

Energy consumption and production can have significant environmental impacts, affecting climate change, air quality, and natural resources.

What is Law of Conservation of Energy?

Law of Conservation of Energy states that, energy can neither be created nor be destroyed, it can only change its form from one form to another.

What is the SI unit of Energy?

The Energy is defined as the amount of workdone by an object and the SI unit of the energy is Joule(J).

What is Commercial unit of energy?

The commercial unit of energy is Kilowatt-hour (kWh).