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Difference Between Solenoid and Bar Magnet

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Solenoid and Bar Magnet Reactions Examples : Introduction

A fascinating phenomenon, magnetism has practical uses in everything from the technology we use to the medical diagnoses we rely on. Solenoid and bar magnets are two fundamental parts of the magnetism universe. Solenoids, which are wire coils that conduct electric current, and bar magnets serve important roles in a variety of applications, including magnetic locks and medical imaging equipment like magnetic resonance imaging (MRI) machines.

To grasp solenoids' and bar magnets' functions and how they contribute to the creation and manipulation of magnetic fields, it is essential to know their distinctions. In this article, we will explore the definitions, go into the mathematical ideas, emphasise the differences, and talk about the reactions and uses of solenoids and bar magnets.


A solenoid is a long coil of wire that is tightly wound in a helical shape.It is frequently constructed using a conductivity material, like copper. A magnetic field is created along the axis of the solenoid when an electric current is sent through the wire. A bar magnet's magnetic field and a solenoid's magnetic field are similar in nature.

Characteristics of Solenoid:

The characteristics of the solenoid are as follows:

  • Controlling the electric current that passes through a solenoid allows for an on/off switch.

  • The size of the electric current and the number of coil turns in a solenoid are directly inversely related to the intensity of the magnetic field it generates.

  • A solenoid has a homogeneous magnetic field that runs parallel to the coil's axis.

  • With field lines flowing from the North Pole to the South Pole, the magnetic field outside the solenoid resembles that of a bar magnet.

Mathematical Terms and Examples:

The magnetic field inside a solenoid can be mathematically described by Ampere's Law. According to Ampere's Law, the magnetic field strength (B) inside a solenoid is directly proportional to the product of the number of turns in the coil (N) and the current flowing through it (I), and inversely proportional to the length of the solenoid (L).

$\frac{ \mu _{\circ }NI}{l}$

An electromagnetic relay is a real-world illustration of a solenoid. A solenoid coil controls the motion of a switch in an electromagnetic relay by adding or withdrawing electric current. The solenoid coil generates a magnetic field that draws a metal armature and causes the switch to close or open as electricity runs through it. Electronic gadgets, automobile systems, industrial control systems, and other applications all often employ electromagnetic relays.

Bar Magnet:

A bar magnet is a cylindrical or rectangular piece of ferromagnetic material, such iron or steel. It has two poles, one each at its ends: the North and South poles. Magnetic field lines, which depict the magnetic field created by a bar magnet, go from its North pole to its South pole.

Characteristics of Bar Magnet:

  • A bar magnet's magnetic field is fixed and cannot be readily adjusted or switched on and off.

  • A bar magnet's size and material composition both affect the strength of its magnetic field.

  • A bar magnet's magnetic field is greatest close to its poles and progressively becomes weaker as you travel away from them.

  • Like poles repel one another whereas opposing poles attract in bar magnets, which contain two poles.

Example of Bar Magnet:

A compass needle is an everyday illustration of a bar magnet. A tiny, freely rotating bar that is magnetised makes up a compass. The bar magnet's North pole aligns with the Earth's magnetic field, causing the compass needle to point in the direction of the magnetic North pole of the planet. This characteristic of bar magnets is useful for orienteering, direction finding, and other outdoor activities.

Difference between Solenoid and Bar Magnet:

Bar magnets are straight pieces of magnetic material with fixed North and South poles, whereas solenoids are cylindrical coils that create a magnetic field when an electric current flows through them. Bar magnets are often employed in compasses and other magnetic devices, but solenoids are flexible and have been used in many electrical and electronic systems. The table describes the difference between the solenoid and bar magnets:

Sl. No



Bar Magnet



A solenoid is a coil of wire coiled into a helical pattern that, when an electric current flows through it, creates a magnetic field.

A bar magnet is a piece of magnetic material that is straight and contains two distinct poles, North and South, as well as a magnetic field.


Shape and Structure

Solenoids are typically cylindrical in shape, consisting of a tightly wound coil of wire.

Bar magnets are elongated and rectangular in shape, with a North pole at one end and a South pole at the other.


Magnetic Field

A solenoid generates a magnetic field that is concentrated inside the coil and resembling a bar magnet. Inside the solenoid, it is powerful, while outside, it is just somewhat weak.

A bar magnet's magnetic field stretches from one pole to the other, producing a relatively consistent magnetic field all around it.


Magnetic Strength

A solenoid's magnetic field can be made stronger by adding turns to the coil, increasing the current that flows through it, or utilising a magnetic core material.

The strength of a bar magnet's magnetic field is determined by the material it is made of and its size. It is relatively constant and cannot be easily adjusted.


Magnetic Polarity

The polarity of a solenoid can be changed by reversing the direction of the current flowing through the coil.

The polarity of a bar magnet is fixed, with one end being the North Pole and the other end being the South Pole.



Electric locks, doorbells, actuators, magnetic resonance imaging (MRI) equipment, electric locks, and other devices all employ solenoids in various ways.

Compasses, electric motors, generators, magnetic storage units, and magnetic separators are all devices that use bar magnets.

Solenoid and Bar Magnet Reactions:

There will be a question in your mind that what is solenoid and bar magnet reaction, what are the examples of reactions of the solenoid and bar magnets? The answer would be that the bar magnets and solenoids react differently to magnetic fields, with different practical implications. Electric motors, relays, and speakers are examples of electromagnetic devices that frequently use solenoids. A solenoid's magnetic field can be changed by adjusting the current that flows through it, allowing for precise movement and control. Comparatively, bar magnets are frequently employed in compasses, magnetic stirrers and refrigerator magnets. They have a constant magnetic field that either interacts with other magnetic materials or is in line with the magnetic field of the Earth.

Solenoid and bar magnet reactions examples have various applications. One of the example is an electromagnetic relay. In this device, a solenoid coil generates a magnetic field when an electric current passes through it. This magnetic field attracts or repels a movable iron armature, causing it to switch the position of electrical contacts and control the flow of current. On the other hand, a compass utilizes a bar magnet to demonstrate the reaction of a magnetic needle. The needle aligns itself with the magnetic field of the bar magnet, exhibiting the attraction and alignment of opposite magnetic poles. These examples highlight the diverse applications and characteristics of the solenoid and bar magnet reactions in various systems.


The article examined solenoids and bar magnet reactions and properties. When electricity passes through a solenoid, a magnetic field is created that has the power to either attract or repel other magnetic materials. Additionally, it demonstrates electromagnetic induction, which causes neighbouring conductive materials to conduct electricity. A bar magnet, on the other hand, has fixed North and South poles that serve as a reference for compasses, align magnetic domains, and deflect charged particles. We can use solenoids and bar magnets in a variety of applications, from electromagnets and generators to compass navigation and particle accelerators, by understanding their special features.

Last updated date: 25th Sep 2023
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FAQs on Difference Between Solenoid and Bar Magnet

1. Can a solenoid be used to generate electricity?

Yes, a moving magnet or a changing magnetic field near a solenoid can induce an electric current in the coil.

2. Is it possible to demagnetise a bar magnet?

Yes, under specific circumstances, such as exposing it to extremely high temperatures or powerful magnetic fields in the opposite direction, a bar magnet can lose its magnetic qualities. The term "demagnetization" refers to this action.

3. Can solenoids and bar magnets be used for wireless power transfer?

Bar magnets alone are not appropriate for wireless power transmission as they do not produce the alternating current or changing magnetic field needed for effective energy transfer. Solenoids, on the other hand, can be utilised for wireless power transfer by inducing an electric current in a receiving coil.