The Characteristics of Electromagnets: Working Principle and Magnetic Fields
Content of tables:
Chapter 1 : The Relationship Between Electromagnets and Magnetic Fields
Chapter 2 : The Electromagnet structure
Chapter 3 : Electromagnet / Solenoid Working Principle
Chapter 4 : Advantages of solenoid
Chapter 5 : Applications of Magnetic Fields
Chapter 6 : The Types of Electromagnets We Design & Supply
Chapter 7 : The Future trends
Chapter 1. The Relationship Between Electromagnets and Magnetic Fields
The electromagnet of magnetic field is an invisible and not real physical phenomenon. It is not composed of chemical substances but is an energy field created by the movement of electric charges, it has a wave-particle duality. Magnetic fields can interact with one another, creating forces even without direct contact—this is the essence of magnetic force.
The electromagnet of magnetic filed forms from electric current. When the electric current or the DC current goes through a wired copper coil, it creates a magnetic field around the coil. If soft iron or silicon steel (ferromagnetic materials) is built inside the coil as a core, the magnetic field is greatly strengthened, making the solenoid magnetic with energized on and magnetism is off, when the current is turned off.
Chapter 2. The Electromagnet structure
The electromagnet is consists of:
solenoid Coil (Winding): Made of wound conductive copper wire; produces a magnetic field with energized.on.
Housing: it usually make of soft iron or silicon steel; significantly increased the magnetic field.
Plunger (Moving Iron Core): A movable part that is attracted by magnetic force to operate mechanical devices.
Spring: it used to return the plunger back to its original position when power is off.
Common shapes of electromagnets/solenoid include frame type, round holding type, and tubular types, chosen based on application needs.
Chapter 3. Electromagnet / Solenoid Working Principle
When the solenoid coil is energized, the iron core becomes magnetized, forming a pair of opposite magnetic poles and producing electromagnetic attraction.
If the electromagnetic force exceeds the spring’s restoring force, the plunger is pulled toward the core to perform mechanical action.
When the current is reduced below a certain level or cut off, the magnetic field will be off, and the spring will let the plunger back to its original position.
The magnetic field strength is directly related to:
The number of copper coil turns
The bigger or less of the electric current
The permeability of the core or housing material
Chapter 4. Advantages of solenoid
the solenoids have a lot of advantage over the permanent magnets, it let them have highly versatile in industrial, scientific, and daily device applications. Some key benefits include:
Switch on/off Operation
solenoid can be turned on and off by design or added a control PCBA board, allowing precise control over when a magnetic field is active.
Magnetic Strength adjustable
By changing the current or the number of coil turns, the magnetic field strength can be adjusted to fit different requirements. Permanent magnets, with contrast, have a fixed magnetic field that cannot be easily changed in force.
Inexpensive
For project applications, solenoid are often less expensive than a permanent magnet of the same size. it typically require fewer raw materials, since the strength is generated through electric current rather than rare or costly magnetic materials.
Design Flexibility
The same solenoid design can be configured to provide different levels of magnetic force simply by changing the input current. This adaptability reduces the need for multiple magnet types in various applications
Chapter 5. Applications of Magnetic Fields
Magnetic field—whether produced by permanent magnets or electromagnet—play a key role in modern technology and industry. In particular, electromagnet is widely used because of their controllable and adjustable nature. Common applications include:
Industrial Machinery
Cranes and lifting equipment use large electromagnets to move heavy steel and scrap metal.
Sorting machines separate magnetic materials from non-magnetic ones.
Transportation
Electromagnetic brakes in trains and roller coasters provide safe, controlled stopping power.
Maglev trains rely on strong electromagnets to achieve frictionless, high-speed travel.
Medical Technology
MRI machines (Magnetic Resonance Imaging) use powerful electromagnets to create detailed body scans.
Magnetic therapy devices and biomedical instruments also employ controlled magnetic fields.
Electronics and Communication
Speakers, microphones, and electric motors depend on electromagnets to convert electrical signals into motion or sound.
Transformers and relays rely on electromagnetic induction to regulate current flow in power systems.
Research and Development
Particle accelerators use strong electromagnets to bend and focus charged particles.
Magnetic confinement in fusion research relies on controlled fields to contain plasma.
Chapter 6 The Types of Electromagnets We Design & Supply
6.1 Solenoid Coil:
A solenoid coil is an important component that converts electrical energy into linear motion. It is typically composed of copper wire wrapped around a hollow plastic bobbin or tube. When current passes through the coil, a magnetic field is generated.
By placing the coil above a ferromagnetic core (typically a magnetic 430F stainless steel armature), the magnetic field forces the plunger upward into the coil. This movement creates an opening or closing action within the valve. Through this mechanism, solenoid coils can be used to operate:
Direct-acting solenoid valve
Auxiliary lift solenoid device
Servo/pressure-assisted solenoid device or solenoid valve
6.2 Standard Electromagnets (Energise-to-Hold Electromagnets/Electro-holding magnets)
The power-on to hold electromagnet clamps only for as long as the electric current is applied. Energise it and it holds; as soon as the current is turned off, the electromagnet stops clamping. The Energise-to-Hold electromagnet is a standard electromagnet concept – a solenoid (wound copper coil) within a high quality high permeability iron assembly for high clamping forces and low magnetic losses. The iron cylinder of the Energise-to-Hold Electromagnet is of sturdy design with a bright nickel finish passivized with body mounting.
Push-pull solenoids feature an intelligent magnetic design that delivers a very high holding force while requiring relatively low power input. This kind of the solenoid makes them ideal for heavy-duty applications and situations where low power consumption or minimal heat generation is important.
Like other linear solenoids, push-pull types are on/off actuators that produce force in one direction when energized. To return the plunger to its original position, an external return mechanism—such as a spring or mechanical load—must be provided.
Push-pull solenoids can be manufactured in either frame-type or tubular-type configurations, it calls frame-type solenoid and tubular solenoid allowing adaptation to a wide range of specialized applications.
6.4 latching ( self-locking ) solenoid
A solenoid is an electromechanical device that moves a plunger with powered on. A latching solenoid provides the same linear motion but features with a mechanism to hold the plunger in place without continuous power.
The latching action can be achieved with residual magnetism or, as this article focuses on, with permanent magnets. This design saves energy and extends service life because power is only required to change the position of the plunger, not to maintain it.
In addition to linear designs, single latching and bistable rotary solenoids are also available for applications requiring rotary motion.
6.5 solenoid valve
A solenoid valve is an electromechanical device used to control the flow of fluids such as water, gas or oil in a pipe. It depends on an electric current to turn on or close the valve by the mechanism.
the normal solenoid valve usually makes of three main components:
Solenoid Coil – A coil of wire generates a magnetic field when current flows through it.
Plunger - The movable part inside the coil that is attracted or repelled by the magnetic field.
Valve Seat - The opening through which fluid flows, which is blocked or open depending on the position of the plunger.
When the solenoid valve is power on, the solenoid coil generates a magnetic field, pulling the plunger and allowing the fluid to flow. When power is turn on, the magnetic field is gone , and the spring or other mechanism pushes the plunger back, or closing the valve and stopping the fluid flow again
Chapter 7. The Future trend
The traditional electromagnets are limited by it’s materials and coil heating, which cap their maximum magnetic field strength. With the discovery and application of superconducting materials, future electromagnets may overcome these limitations, achieving stronger magnetic fields and lower energy consumption. With continuous innovation, solenoids are expected to find even broader applications through all of industries, thanks to it simple structure, reliable operation, and ease of integration into automated systems.