Physics
Ravi observed that an electromagnet could lift iron pieces only when electric current was flowing through it. When the current was switched off, the iron pieces fell down.
(a) Why does an electromagnet lose its magnetism when the current stops?
(b) How is an electromagnet different from a permanent magnet?
(c) How can the strength of an electromagnet be increased?
(d) Why are electromagnets preferred in cranes?
(e) Which material is preferred for making the core of an electromagnet?
Magnetism
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Answer
(a) An electromagnet produces magnetism only when electric current flows through its coil. When the current is switched off, the magnetic field disappears, so the electromagnet loses its magnetism.
(b) An electromagnet is a temporary magnet that works only when current flows through it, and its strength can be controlled. A permanent magnet, on the other hand, has permanent magnetism and does not require electric current. Its strength cannot be controlled.
(d) Electromagnets are preferred in cranes because their magnetism can be switched on and off. This allows heavy iron objects to be lifted easily and released when required.
(e) Soft iron is preferred for the core of an electromagnet because it gets magnetized easily and loses its magnetism quickly when the current is switched off.
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