Electromagnet vs Permanent Magnet: Key Differences, Uses & Examples
Magnetism plays a major role in modern technology and JEE Main Physics. Understanding the difference between electromagnet and permanent magnet is crucial, since these forms of magnetism power key devices and solve distinct engineering problems. Both create a magnetic field, but the physics behind them is fundamentally different.
Magnets are materials or devices that produce a magnetic field. They can attract ferromagnetic substances like iron and nickel. There are chiefly two types: permanent magnets that possess natural magnetism, and electromagnets that require electric current. Knowing their construction, field pattern, and uses is key for JEE Main.
Definition: Difference Between Electromagnet and Permanent Magnet
- Electromagnet: Temporary magnet created by passing current through a coil wound on a soft iron core.
- Permanent magnet: Material that maintains lasting magnetism, created during manufacture by aligning domains.
- Electromagnetism follows Oersted’s law and depends on current. Permanent magnets rely on internal material properties.
- Key exam distinction: Electromagnet needs current; permanent magnet does not.
Tabular Comparison: Difference Between Electromagnet and Permanent Magnet
| Criteria | Electromagnet | Permanent Magnet |
|---|---|---|
| Magnetic Field Source | Produced by electric current | Inherent in material |
| Magnetism Type | Temporary; exists only when current flows | Permanent; persists without power |
| Control over Strength | Easily adjustable (via current/turns) | Fixed after manufacture |
| Polarity | Can be reversed by changing current direction | Fixed and cannot be reversed easily |
| Core Materials | Soft iron core | Hard magnetic materials (steel, alnico) |
| Field Strength | Can be very strong | Usually weaker than electromagnet |
| Demagnetisation | Rapid (when current stops) | Very slow or negligible |
| Examples | Electric bell, crane magnet | Compass, refrigerator magnet |
This table summarizes the difference between electromagnet and permanent magnet by examining source, strength, control, and real-world use. It is ideal for revision and helps avoid common exam mistakes.
Construction and Working of Electromagnet and Permanent Magnet
- Electromagnet construction: Coil of insulated copper wire wound around a soft iron core. Direct current (DC) is passed through the coil.
- Soft iron core enhances the field due to high magnetic permeability.
- Permanent magnet construction: Made by magnetising hard steel or alloys using strong external magnetic fields.
- Their domains are aligned permanently during manufacture, making the magnetism last for years.
When current flows in an electromagnet, the magnetic field forms per the Biot-Savart law and right-hand thumb rule. If the current stops, the field vanishes. For permanent magnets, the internal structure causes domains to stay aligned even without current, maintaining a steady magnetic field.
Schematic diagrams for both device types are a common JEE Main question. Always draw labeled coils, core, and indicate current direction for electromagnets. For permanent magnets, show “N” and “S” poles clearly.
Applications: Where Are Electromagnets and Permanent Magnets Used?
- Electromagnets: electric bells, relays, loudspeakers, magnetic cranes, MRI machines, particle accelerators.
- Permanent magnets: compasses, door latches, refrigerator seals, toy motors.
- Electromagnets are preferred for devices needing strong, controllable, or reversible fields.
- Permanent magnets save energy when continuous power is wasteful.
For example, in a relay switch, electromagnets allow precise switching by controlling current. Permanent magnets are ideal where reliability and no power consumption are crucial, such as in magnetic compasses or certain sensors.
Magnetic materials choice is crucial. See the magnetic effects of current and magnetism for more about JEE-relevant field calculations and material selection.
Similar Magnetic Concepts and Pitfalls in Exam Answers
- Solenoids alone are not magnets; they become electromagnets when carrying current and a soft iron core is present.
- Bar magnets are permanent magnets with fixed poles.
- Temporary magnets lose their magnetism quickly; don’t confuse with soft iron cores in electromagnets.
- Domain alignment is permanent in permanent magnets but reversible in electromagnets.
- Reversing current in an electromagnet swaps north and south poles, a key difference from permanent magnets.
Be careful not to confuse difference between electromagnet and permanent magnet with magnetic and non-magnetic materials. This is a classic JEE pitfall.
Always refer to NCERT textbooks and Vedantu JEE Physics pages for updated concepts. Practice drawing neat diagrams and writing answers in bullets to score maximum marks.
Worked Example: Electromagnet vs Permanent Magnet in Real Life
A JEE Main problem asks: Why is an electromagnet used in an electric crane in scrapyards, not a permanent magnet?
- Scrapyard cranes need to pick up and release heavy iron parts quickly.
- Electromagnet’s strength is large and can be switched off by cutting current.
- Permanent magnets would not release the iron load easily; no on-off control.
- Thus, only electromagnets provide safe, controllable lifting in this scenario.
Final answer: Electromagnet’s field can be turned off, so it is preferred in cranes. This key feature separates it from a permanent magnet.
For extra practice, try these JEE challenges: Calculate the magnetic field strength for a coil-iron-core electromagnet using Biot-Savart law. Compare the field to that of a fridge magnet of similar size.
Keep revising more difference-based topics using Vedantu’s trusted resources for JEE Main Physics. For deep dives, review electromagnetic waves, bar magnet features and properties of magnetic materials.
In summary, grasping the difference between electromagnet and permanent magnet in tabular form, controlling magnet strength, and recognizing real-life examples are vital for JEE Main success.
- Review electric and magnetic field line diagrams for better visualization.
- Visit revision notes on magnetism before the exam.
- Use JEE Physics practice papers to test your understanding.
- Explore electromagnetic induction for deeper insight.
- For foundation clarity, start with JEE Main Physics essentials on Vedantu.
FAQs on Difference Between Electromagnet and Permanent Magnet Explained
1. What is the difference between an electromagnet and a permanent magnet?
The main difference is that an electromagnet produces a magnetic field only when an electric current flows through it, while a permanent magnet has an inherent, lasting magnetic field.
Key points include:
- Electromagnet: Magnetism is temporary and controlled by electric current.
- Permanent Magnet: Magnetism is constant and does not require electricity.
- Electromagnet strength can be changed; permanent magnets have fixed strength.
2. Why are electromagnets preferred over permanent magnets in some devices?
Electromagnets are preferred because their magnetic strength can be easily switched on, off, or adjusted by controlling the electric current.
Main reasons:
- The magnetic field is controllable and can be made very strong.
- Electromagnets can be turned off when not needed, saving energy and preventing unwanted attraction.
- Used in devices like electric bells, MRI machines, cranes, and relays where variable, safe magnetism is essential.
3. How is an electromagnet made?
An electromagnet is made by winding a wire coil around a soft iron core and passing electric current through the coil.
Steps:
- Take a soft iron rod (core).
- Wrap it with insulated copper wire in a coil form.
- Connect both ends to a battery or power source.
- The iron core becomes magnetic as long as current flows.
4. Which is stronger: electromagnet or permanent magnet?
An electromagnet can be much stronger than a permanent magnet, because its strength depends on the current and number of coil turns.
- Electromagnet: Strength can be increased by raising current or adding more turns to the coil.
- Permanent Magnet: Has a fixed strength determined by its material.
5. What materials are required to create an electromagnet?
To create an electromagnet, you need:
- Soft iron core (best material for strong field, sometimes steel is used but iron is preferred)
- Insulated copper wire (for winding the coil)
- Source of electric current (battery or power supply)
These materials help convert electricity into magnetism.
6. Can a permanent magnet become an electromagnet if current passes through it?
No, a permanent magnet cannot become an electromagnet simply by passing current through it.
Explanation:
- Permanent magnet already has fixed, natural magnetism.
- Electromagnetism is generated in special soft iron and wire coil set-ups, not in solid permanent magnets.
- Passing current through a permanent magnet may affect its field, but does not change its fundamental type.
7. How does the magnetic field of an electromagnet differ from that of a permanent magnet?
The magnetic field of an electromagnet can be switched on/off and made stronger or weaker by changing the electric current.
- Electromagnet field: Exists only when current flows; adjustable.
- Permanent magnet field: Constant; always present and cannot be changed easily.
8. What are real-life examples of electromagnets and permanent magnets?
Real-life examples help differentiate both magnet types:
- Electromagnets: Used in electric bells, MRI machines, cranes, loudspeakers, motors, relays.
- Permanent magnets: Found in refrigerator magnets, compasses, magnetic locks, microphones, and speakers.
These examples are frequently asked in board and entrance exams.
9. Does heating an electromagnet and a permanent magnet affect their magnetism differently?
Yes, heating affects electromagnets and permanent magnets differently.
- Permanent magnets: Heating can weaken or even destroy their magnetism permanently (reaching the Curie temperature).
- Electromagnets: Heating affects only the core temporarily, as magnetism returns with current after cooling, unless the core material is damaged.
10. What is the main reason why an electromagnet loses its magnetism when the current is switched off?
An electromagnet loses its magnetism immediately when the current is switched off because its magnetic field is generated by flowing electric current.
- Magnetism is temporary and relies on electricity.
- Unlike permanent magnets, there is no constant, intrinsic magnetism without current.
