Main Characteristics and Uses of Electromagnets vs Permanent Magnets
The Difference Between Electromagnet And Permanent Magnet is a key topic in physics exams, as it helps students understand magnetic materials and their technological applications. Knowing these differences is important for solving questions in board exams and competitive exams like JEE or NEET.
Definition of Electromagnet
An electromagnet is a type of temporary magnet made by winding an insulated wire around a soft iron core, with magnetism generated only when electric current flows through the coil.
The magnetizing effect in an electromagnet depends on the magnitude and direction of the electric current supplied. For further understanding of related physics concepts, see Difference Between Current And Voltage.
Definition of Permanent Magnet
A permanent magnet is a material that maintains its magnetic properties even without any external electric current, often made from substances such as steel or alnico alloys.
Permanent magnets have fixed strength and polarity that cannot be altered by external electric supply. These are used in applications requiring constant magnetic fields, unlike electromagnets.
Difference Table
| Electromagnet | Permanent Magnet |
|---|---|
| Temporary magnetism, only when current flows | Permanent magnetism, independent of current |
| Made from soft iron core | Made from hard magnetic materials |
| Magnetism can be turned on or off | Magnetism cannot be switched off |
| Strength can be varied by changing current | Strength is fixed and constant |
| Polarity can be reversed by reversing current | Polarity is always fixed |
| Usually stronger magnetic field possible | Generally lower field strength |
| Loses magnetism when current stops | Retains magnetism for a long duration |
| Not suitable as compass needle | Suitable for compass needles |
| Low retentivity and coercivity | High retentivity and coercivity |
| Electrically controlled device | No electrical control required |
| Used in electric bells, relays, motors | Used in loudspeakers, microphones, fridge doors |
| Core must be soft iron for easy demagnetization | Core is hard steel or alloys for permanent effect |
| Energy consumed only when active | No energy consumption required for magnetism |
| Size and shape can be easily varied | Size and shape change affects properties |
| Used in temporary lifting equipment | Used in permanent fixtures and tools |
| Easy to demagnetize by interrupting current | Requires special methods to demagnetize |
| Affected by variations in electric supply | Unaffected by electrical fluctuations |
| Not used in devices requiring stable field continuously | Preferred for continuous field requirements |
| Assembly requires coil and power source | No external assembly or power source |
| Stronger in short duration, adjustable | Reliably stable, long-term usage |
Key Differences
- Electromagnet needs electric current to work
- Permanent magnet works without electric current
- Electromagnet strength and polarity are variable
- Permanent magnet strength and polarity are fixed
- Electromagnets are temporary and easily altered
- Permanent magnets are stable and long-lasting
Examples
A classic example of an electromagnet is the coil inside an electric bell, which produces a magnetic field only when current passes through it.
A bar magnet used for holding refrigerator doors is an example of a permanent magnet.
Applications
- Electromagnets are used in motors and transformers
- Permanent magnets are found in magnetic compasses
- Electromagnets enable maglev trains and relays
- Permanent magnets are used in sensors and speakers
- Electromagnets are suitable for scrapyard lifting cranes
- Permanent magnets are used in refrigerators and toys
One-Line Summary
In simple words, Electromagnet produces temporary magnetism using current, whereas Permanent Magnet shows constant magnetism without electricity.
FAQs on What Is the Difference Between an Electromagnet and a Permanent Magnet?
1. What is the difference between an electromagnet and a permanent magnet?
Electromagnets and permanent magnets differ mainly in how they produce magnetic fields and in their ability to switch magnetism on or off.
Key differences:
- Electromagnet: Generated by electric current; can be switched on/off; magnetic strength can be controlled.
- Permanent Magnet: Naturally magnetic; produces a constant magnetic field; cannot be easily turned off or altered.
2. How is an electromagnet made?
An electromagnet is created by passing an electric current through a coil of wire wound around a core, usually made of soft iron.
Steps to make an electromagnet:
- Wrap insulated copper wire around an iron nail or rod.
- Connect the wire ends to a battery or power source.
- The core becomes magnetic when current flows through the coil.
3. Why can the strength of an electromagnet be changed but not that of a permanent magnet?
The strength of an electromagnet can be adjusted by changing the current, number of coil turns, or core material, while a permanent magnet’s strength is fixed by its material.
For electromagnets:
- Increase current to increase strength.
- Use more wire turns or better core material.
- Turn off the power to demagnetize.
4. List two advantages of electromagnets over permanent magnets.
Electromagnets offer flexibility and control in applications where changing magnetic fields are required.
Main advantages:
- Their magnetic strength can be increased or decreased easily.
- They can be switched on and off as needed for industrial and scientific uses.
5. How does a permanent magnet differ from an electromagnet in terms of material used?
Permanent magnets use special alloys (like Alnico, neodymium), while electromagnets use soft iron as a core for temporary magnetism.
Permanent Magnet Material: Made from hard magnetic materials with lasting magnetism.
Electromagnet Material: Uses easily magnetized and demagnetized soft iron.
6. In which situations would you prefer an electromagnet over a permanent magnet?
Electromagnets are preferred when variable magnetism or controlled switching on/off is needed.
Common uses:
- Electric bells and relays.
- Cranes for lifting scrap metal.
- Electric motors and generators.
- Magnetic locks and medical devices.
7. What makes a permanent magnet permanent?
Permanent magnets retain their magnetism because they are made from materials with a strong retentivity and coercivity, which keeps their atomic domains aligned.
- Made from hard magnetic substances.
- Atomic structure prevents randomization of magnetic domains under normal conditions.
8. Can a soft iron bar be used as a permanent magnet? Why or why not?
No, a soft iron bar cannot be used as a permanent magnet because it loses its magnetism quickly once the magnetizing force is removed.
- Soft iron is suitable for electromagnets, not permanent magnets.
- It is easily magnetized and demagnetized, not suitable for lasting magnetism.
9. What are some everyday applications of electromagnets and permanent magnets?
Electromagnets and permanent magnets are widely used in daily life for various functions.
Applications of Electromagnets:
- Electric bells
- Motors and generators
- Magnetic levitation trains
- Relays and cranes
- Refrigerator doors
- Speakers and microphones
- Compass needles
- Magnetic locks
10. What happens if the electric current to an electromagnet is switched off?
If the electric current is switched off, an electromagnet loses its magnetic property because its field depends on current.
- The core becomes non-magnetic.
- No magnetic force is produced without current.
