In our previous sessions, we have understood the magnet, magnetic materials, and how materials behave in the presence of magnetic fields. We also know about a type of magnet in which the magnetic field is produced by an electric current. Those magnets are known as electromagnets. In this session, let us learn in detail about a type of electromagnet known as a solenoid.
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What Is a Solenoid?
Electromagnets
Electromagnets are the kind of magnet where the wire is wrapped around an iron core. Upon the supply of electric current, a magnetic field is created around the iron core. The magnetic field vanishes when the electric supply is cut off. The core of the magnet that is wound by wires is ferromagnetic or ferrimagnetic in nature. Iron is the most commonly used material in the core.
The magnetic field established is controlled by the supply of electricity. A permanent magnet does not need the supply of power, and the magnetic field cannot be controlled. Electromagnets are used in making solenoids, MRI machines, hard disks, relays, motors, loudspeakers, and generators.
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Now that we have understood electromagnets, let us learn about solenoids.
The solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The solenoid is as shown in the figure below. The solenoid is a coil of wire, and the plunger is made of soft iron. The magnetic field is formed around the coil when an electric current passes through it and draws the plunger in. We can say that the solenoid is responsible for converting electrical energy into mechanical work.
Solenoids were the results of the development of an efficient and greater strength offering magnets. In the year 1823, a French Physicist and a mathematician, Andre-Marie Ampere coined the term solenoid to designate a helical coil.
Note: Electromagnet with the fixed core is not considered a solenoid.
Working of Solenoids
After understanding the definition of solenoid and its parts, let us learn how solenoids work. Solenoid works on the principle of electromagnetism. When the electric current passes through the coil, the magnetic field is generated. When a metal core is placed inside the coil, the magnetic lines of flux are concentrated on the core. This increases the induction of the coil as compared to the air core. This concept is known as electromagnetic induction.
As we know, coils are made of numerous turns of copper wire wound tightly around it. A strong magnetic flux is developed when the current passes through the wire. The concentration of flux is high on the core, while some of the flux appears at the ends of the coil and outside the coil too. By increasing the flow of electric current or by increasing the density of the turns, the magnetic strength of the solenoid can be increased.
The housing is made of iron or steel. Housing is surrounded by the magnetic field created due to the coil. The plunger lets the mechanical force do work. Solenoids too feature positive and negative poles, through which an object can be attracted or repelled.
Consider a solenoid whose length is more than the radius. Enameled and insulated wire is wrapped with a wire in the form of a helix with a small gap between the turns. The amount of vector force provided by each turn, and the total magnetic field created by the solenoid are equal to that formed by a circular loop. This gives the total magnetic field of the solenoid. The lines of magnetic fields produced within a finite solenoid are as shown below.
Image below shows the depiction of a solenoid.
The field at any point beyond the solenoid is very thin. The field inside the solenoid is parallel to its axis at all times. The magnetic force produced by a solenoid can be defined using the Law of the Ampere:
Where n is the number of turns of the wire per unit length, I is the current flowing through the wire, and the direction is given using the right-hand thumb rule.
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Watching this Video about Magnetism and Force on Dielectric in Charged Capacitor
Types of Solenoid
Different types of solenoids are as follows:
- AC-Laminated Solenoid
- DC-C Frame Solenoid
- DC-D Frame Solenoid
- Linear Solenoid
- Rotary Solenoid
Let us know about each type of solenoid.
AC-Laminated Solenoid
The AC-laminated solenoid is known for the amount of force that can occur in its first stroke. The AC-laminated solenoid features a metal core and a coil of wire. The core of the solenoid is made with a laminated metal to reduce the stray current. AC-laminated solenoids are capable of using more strokes than DC laminated solenoids. This type of solenoid produces a clean buzzing sound when they operate.
DC C-Frame Solenoid
The DC C-Frame solenoid has one frame in C-shape covered around the coil. The DC C-frame solenoid is said to be DC configuration and can be used in equipment designed for AC power.
Watch the Video and Learn about Magnetic Field Due to Solenoid and Properties of Magnetic Field Lines
DC-D Frame Solenoid
DC-D frame solenoid is a two-piece frame covering the coil. It has a controlled stroke operation and can be used with AC power too.
Linear Solenoid
Linear solenoid features a coil of wire wrapped around movable metalcore. It aids in applying pulling or pushing force to a mechanical device. The linear solenoid is used in starting devices. This mechanism aids in completing a circuit and letting current flow through.
Rotary Solenoid
The rotary solenoid is used in the automatic control process. This solenoid also features a coil and a core, but it has a different operation.
Applications of Solenoid
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They are used in construction, agricultural vehicles, speciality vehicles, and industrial equipment.
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Linear solenoids are used in highly secured door mechanisms
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They are used in starter motors of bikes and cars.
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It is used in gaming machines, scanners, printers, circuit breakers, and photographic shutters.
Read more: Solenoid and toroid
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See the Video below to Know in Detail about the Solenoid
Frequently Asked Questions – FAQs
What Is a solenoid?
Solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix.
What are the types of solenoids?
The following are the types of solenoids:
- AC-Laminated Solenoid
- DC-C Frame Solenoid
- DC-D Frame Solenoid
- Linear Solenoid
- Rotary Solenoid
State true or false: Electromagnets are not used in making solenoids.
Using the law of the ampere, how is the magnetic force produced by a solenoid defined?
The magnetic force produced by a solenoid is defined as:
List some of the applications of electromagnets.
Electromagnets are used in MRI machines, hard disks, solenoids, relays, motors, loudspeakers, and generators.
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