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Electromagnets and permanent magnets are two types of magnets that differ in terms of their magnetic fields. As easily noticeable from their names, permanent magnets are magnets having a fixed magnetic field and electromagnets, on the other hand, have a temporary magnetic field which entirely depends on the electric current which flows through it.
| Table of Content |
Key Takeaways: Permanent magnet, Electromagnet, magnetic strength, magnetic field, electric current, Ferrite, Aluminium, Nickel, Cobalt
Premanent Magnet
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A permanent magnet is a type of magnet with already existing magnetic properties due to the magnetic strength it possesses. A permanent magnet always readily shows magnetic properties, and the magnetic strength of a permanent magnet is determined by the material it is made up of. Also, these magnets do not require electric current for their magnetic properties. Permanent magnets are usually made up of materials like Ferrite, Aluminium, Nickel, Cobalt (AlNiCo), etc. A bar magnet is an example of a permanent magnet.
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Electromagnet
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Often known as a non-permanent magnet, an electromagnet does not possess a magnetic field of its own. An electromagnet depends on electric current for its magnetic strength. An electromagnet is usually made up of a wire in a coil. As soon as the electric current stops, an electromagnet stops working. Moreover, the magnetic strength of an electromagnet can be altered by changing the electric current that passes through it. The solenoid is a common example of an electromagnet.
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Difference between Electromagnets and Permanent magnets
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The major difference between these two magnets is the magnetic strength that they offer because of their properties. Let us understand how electromagnets and different from permanent magnets in the table below:
| Properties | Permanent Magnets | Electromagnets |
|---|---|---|
| Magnetic Strength | The magnetic strength of permanent magnets is fixed and depends on the material they are made up of | Magnetic strength of an electromagnet can be altered through the amount of electric current passed through it. |
| Magnetic Properties | Permanent magnets display fixed magnetic properties that cannot be changed. | These types of magnets display magnetic properties only when electric current passes through them. |
| Electric current | Nothing happens when electric current passes through permanent magnets | Electric current directly increases/decreases an electromagnet'S magnetic properties. |
| Magnetic Poles | Permanent magnets have fixed magnetic poles which cannot be altered. | The magnetic poles of an electromagnet can be interchanged. |
Things to Remember
- Electromagnets and permanent magnets are two types of magnets that differ in terms of their magnetic fields. As easily noticeable from their names, permanent magnets are magnets having a fixed magnetic field, electromagnets, on the other hand have a temporary magnetic field which entirely depends on the electric current which flows through it.
- The major difference between both of these magnets is because of their magnetic field strength.
- Magnetic poles of electromagnets can be interchanged whereas magnetic poles of permanent magnets cannot be interchanged.
- Electromagnets respond to electric current whereas permanent magnets do not.
- Permanent magnets are used in computers, headphones, whereas electromagnets are used in fans, blenders, vacuums etc.
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Sample Questions
Ques. Which of the magnets given below contains a soft iron and why? (2 marks)
a) Bar magnet
b) Permanent magnet
c) Electromagnet
c) Temporary magnet
Ans. c. Electromagnet
An electromagnet contains a soft iron piece so as to develop its magnetic properties when electric current passes through it.
Ques. Write advantages and disadvantages of electromagnets. (5 marks)
Ans. Advantages of electromagnets:
- Electromagnets are easy to build and are really inexpensive.
- Electromagnets are lightweight and can be used easily.
- Electromagnets can interchange their poles, which is useful in discontinuing the magnetic field whenever necessary.
Disadvantages of Electromagnets:
- Electromagnets can heat up really fast and therefore can lose the electric current, and so the electric field.
- For a continuous magnetic supply, a continuous electric supply is needed, which is only possible due to large coils, which take up very much space.
- Electromagnets can also cause short circuits.
Ques. Write advantages and disadvantages of permanent magnets. (5 marks)
Ans. Advantages of Permanent magnets:
- No electric current is needed to induce a magnetic field.
- Permanent magnets have a permanent magnetic field which can never decrease.
Disadvantages of permanent magnets:
- Permanent magnets tend to corrode and so their maximum magnetic strength cannot be reached.
- Poles of permanent magnets cannot be interchanged
- Permanent magnets cannot be used for hot applications, as they only work under a specific temperature.
Ques. What are permanent magnets? Explain briefly, with an example. Is steady current the only source to induce magnetic field? (3 marks)
Ans. Permanent magnets are substances which retain a fixed magnetic field at room temperature. These are usually made up of hard materials, which do not depend on external factors to retain their magnetic properties. Example of a permanent magnet is a bar magnet.
No, magnetic fields can also be altered through unsteady current, which creates a temporary magnet. Moreover, permanent magnets are themselves a source of magnetic field.
Ques. List two important characteristics required to make a permanent magnet. Why is the core of an electromagnet made up of only ferromagnetic materials? (4 marks)
Ans. The two characteristics required to make a permanent magnet are:
- High retentivity so as to maintain and retain its magnetic field
- High coercivity so that it's magnetic field is not disrupted by other stronger magnetic fields.
Ferromagnetic materials make sure that a high magnetic field and a high magnetic strength is created even when a small current passes for a shorter duration.
Ques. Write three important characteristics required to make a permanent magnet. (2 marks)
Ans. Characteristics to choose while making permanent magnet material:
- High retentivity
- High coercivity
- High permeability
Ques. Write three important characteristics required to make an electromagnets. (2 marks)
Ans. Characteristics to choose while making an electromagnet:
- Low retentivity
- Low coercivity
- High permeability
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