• ### Browse All Lessons

##### Assign Lesson

Help Teaching subscribers can assign lessons to their students to review online!

 Tweet

# Magnetic Field and Energy

Introduction
We often think of force as a push or a pull, and we believe that one object pushes or pulls another by touching it. But the interesting fact is that one object can push or pull another one without any direct contact. A force that can act over a distance without touching is explained by fields that can surround an object and exert force on another object within that specific area. Understanding the relationship between the magnetic field and energy is important for scientists in many fields such as physics, engineering, geology, etc. In this article, we will explore the relationship between the magnetic field and energy, and the implications of this relationship.

What is a Magnetic Field?
We know that magnets can attract or pull each other, without touching. Magnets are capable to do this because they produce magnetic fields that can push or pull other magnets.

Fig.1 A magnet produces magnetic field that can push or pull

The magnetic field is a region around a magnetic material within which the force of magnetism acts. The magnetic field is a vector field, which means that it has both direction and magnitude. A magnetic field appears as lines that originate from one pole of the magnet and curve around to another pole.  Magnetic field lines are generated by moving electric charges, magnets, and changing electric fields. The magnetic field is measured in units of Tesla or Gauss, and they can be visualized by using magnetic field lines.

Fig.2 Magnet produces magnetic field lines that start from north pole and terminate at the south pole

Properties of Magnetic Field Lines
• These lines never cross each other.
• The density of the magnetic field lines indicates the strength of the field region.
• Magnetic field lines always make continuous, closed loops.
• They always emerge from the north pole and terminate at the south pole.
• The direction of the field is determined by the direction of the magnetic field lines.

Fig.3 Magnetic field lines make continuous, closed loops

What is Energy?
Energy is a basic concept in physics, and it is defined as the ability of something to do work. Work is done when an external force is applied to an object to displace it from its current position. The amount of work done can be calculated with the applied force multiplied by the distance over which the force is applied. Energy is measured in the S.I. unit joule (J), and can exist in many forms such as kinetic energy, potential energy, and thermal energy.

The Relationship Between Magnetic Field and Energy
Magnetic field and energy are intimately connected. There are various ways in which a magnetic field can store and transfer energy.

Through Magnetic Potential Energy
The magnetic field can store energy through magnetic potential energy around a bar magnet or a current-carrying conductor. When the current-carrying conductor or magnet moves in a magnetic field, this stored energy in the magnetic field is converted into kinetic energy.

Through Magnetic Induction
Another common way in which a magnetic field can store energy is through magnetic induction. This takes place when a magnetic field changes over time, it induces an electric field. As a result, the electric field can induce a current in a nearby conductor. This phenomenon is used in transformers and electric generators, where the electricity is generated by using a magnetic field.

Through Electromagnetic Waves
The magnetic fields can also transfer energy with the help of electromagnetic waves. Electromagnetic waves are waves that are generated as a result of vibration between an electric field and a magnetic field that travel through space at the speed of light. These waves are used to carry energy, and they play a crucial role in many applications such as communication, radar, and microwave.

Through Magnetic Forces
There is another way through which a magnetic field can transfer energy i.e. via magnetic forces. When two magnets are brought close together, either force of attraction or repulsion is exerted on the magnets. This force that is experienced by the magnets appears due to the interaction of the magnetic fields around the magnets. The energy stored in the magnetic field is transferred to the magnets whether they move close together or further apart.

Summary
• The magnetic field is a vector field that is defined as a region around a magnetic material within which the force of magnetism acts.
• Magnetic field appears in the form of field lines that always start from the north pole and end at the south pole.
• The magnetic fields can store and transfer energy in various ways including magnetic induction, magnetic potential energy, magnetic forces, and electromagnetic waves.

Images:

Related Worksheets: