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A soft iron rod is placed inside a current-carrying solenoid. The soft iron rod becomes a/an __________.
Permanent magnet
Electromagnet
Insulator
Diamagnetic material
Electromagnet
When a soft iron rod is placed inside a current-carrying solenoid, it becomes an electromagnet. The magnetic field produced by the solenoid magnetizes the soft iron core, significantly increasing the strength of the magnetic field.
When a soft iron rod is placed inside a current-carrying solenoid, it becomes an electromagnet. The magnetic field produced by the solenoid magnetizes the soft iron core, significantly increasing the strength of the magnetic field.
Think of the solenoid as an 'amplifier' for the iron rod; the electricity provides the 'push' to align the iron's internal structure, transforming a common piece of metal into a temporary magnet.
SOFT: Solenoid Overcomes Ferromagnetic Transformation
B=╬╝0тАЛnI тАФ Magnetic field of a long solenoid
╬╝=╬╝rтАЛ╬╝0тАЛ тАФ Magnetic permeability in a medium
The solenoid acts as a temporary magnet while the current flows, creating a magnetic field B=╬╝0тАЛnI. The soft iron core has high magnetic permeability, which allows it to align its internal magnetic domains with the applied field. This phenomenon, known as magnetic induction, drastically concentrates and strengthens the magnetic flux within the rod.
Soft iron is a ferromagnetic material with high magnetic permeability.
Electromagnets are temporary magnets whose strength depends on the current (I) and number of turns (n).
Soft iron loses its magnetism almost immediately when the current is switched off, making it ideal for electromagnets.
Steel is used to make permanent magnets because it retains magnetism (high retentivity).
Magnetic strength can be adjusted by varying the current
Can be turned ON and OFF instantly
Polarity can be reversed by changing the direction of current
Requires a continuous supply of electricity to function
Magnetic field collapses as soon as the power source is removed
Electric bells and relays
Magnetic cranes in scrap yards
MRI machines in hospitals
Soft iron is chosen for electromagnets due to its low retentivity and high permeability.
Option A is incorrect because soft iron does not retain magnetism well enough to be a permanent magnet.
Option C is incorrect as iron is a metal and a conductor.
Option D is incorrect because soft iron is ferromagnetic, not diamagnetic.
B is correct тАФ Placing a soft iron rod inside a solenoid creates an electromagnet because the iron core concentrates the magnetic flux lines produced by the coil.
Remember: For permanent magnets, we use hard materials like steel (high retentivity), whereas for electromagnets, we use soft materials like iron (low retentivity, high permeability).