Meaning and Working
An electromagnets is a temporary magnet produced when electric current passes through a conductor, usually a wire coil.
When current flows through the coil, it generates a magnetic field. If the coil is wound around a soft iron core, the magnetic field becomes much stronger because the core’s magnetic domains align with the field.
The magnetic effect usually disappears or becomes very weak when the current is switched off.
Factors Affecting Strength
The strength of an electromagnet depends mainly on:
- amount of electric current;
- number of turns in the coil;
- nature of the core material;
- shape and size of the coil;
- distance from the electromagnet.
Increasing the current or number of coil turns generally strengthens the magnetic field.
Soft iron is commonly used as the core because it becomes strongly magnetised when current flows and loses most of its magnetism when the current stops.
Electromagnets and Permanent Magnets
| Feature | Electromagnet | Permanent magnet |
| Source of magnetism | Electric current | Magnetic properties of material |
| Control | Can be switched on and off | Cannot normally be switched off |
| Strength | Can be adjusted | Mostly fixed |
| Polarity | Can be reversed by changing current direction | Usually fixed |
| Energy requirement | Requires continuous electricity | Does not require electricity |
| Typical core | Soft iron | Hard magnetic materials |
Electromagnets are preferred where controllable and variable magnetic fields are required.
Applications
Electromagnets are used in:
- electric motors and generators;
- transformers;
- relays and circuit breakers;
- loudspeakers and headphones;
- magnetic cranes for lifting scrap metal;
- magnetic resonance imaging systems;
- electric bells and door locks;
- particle accelerators;
- industrial separation of magnetic materials;
- electromagnetic braking systems.
In an electric motor, electromagnets interact with another magnetic field to generate rotational force.
Advantages and Limitations
Their major advantages include:
- adjustable magnetic strength;
- reversible polarity;
- ability to switch magnetism on and off;
- suitability for automation and precise control;
- production of very strong magnetic fields.
Important limitations include:
- continuous electricity consumption;
- heat generation in the coil;
- loss of magnetism during power failure;
- need for insulation and cooling;
- energy losses caused by electrical resistance.
Superconducting electromagnets can produce extremely strong magnetic fields with very low electrical resistance, but they require very low operating temperatures.
Conclusion
Electromagnets convert electrical energy into a controllable magnetic field. Their adjustable strength and switchable operation make them essential in motors, medical equipment, communication devices and modern industrial systems.
