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# State any two advantages of electromagnets over permanent magnets.  Hint: Strength of electromagnet is variable but strength of permanent magnet is constant.

Complete step by step solution:
The advantages of electromagnets over permanent magnets are mentioned as below
1. We can change the strength of the magnetic field of an electromagnet by varying current. We can either increase or decrease its strength. This is not possible in case of permanent magnets.
2. It is easier to manufacture electromagnet.
3. Magnetic power of electromagnets is more than compared to permanent magnets.

(i) Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole, denoting the centre of the coil.
(ii) The space around a magnet in which its magnetic effect can be experienced is called the magnetic field.
(iii) The SI unit of strength of the magnetic field is Tesla or N/A/m.
(iv) The strength of the magnetic field is also measured in Gauss (G).
Where $1{\text{ }}gauss{\text{ }}\left( G \right) = {10^{ - 4}}tesla{\text{ }}\left( T \right)$
(v) The distance between the two poles of a bar magnet is called the magnetic length of the magnet. It is always less than its geometric length.
(vi) The product of the strength of either pole and the magnetic length of the magnet is called its magnetic dipole moment.

Note: There is one disadvantage of electromagnet; if electrical power is not available then it will not work whereas permanent magnet will work without electrical power.
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