A factory plans to install a powerful electromagnet for lifting metal scraps. To maximize the magnetic field strength around the coil, which of the following combinations would be most effective?
Using a soft iron core, increasing coil turns, and increasing current through the coil
The strength of an electromagnet depends on:
- Core material: A soft iron core has high magnetic permeability and low retentivity — it concentrates field lines efficiently without retaining magnetism when current is off.
- Number of coil turns (N): More turns → stronger magnetic field (B ∝ N).
- Current (I): Greater current → stronger field (B ∝ I).
Combined: B ∝ μ × N × I / length
Using a steel core (option 4) is wrong — steel has high retentivity but lower permeability than soft iron. Copper (option 3) and air core (option 2) give much weaker fields.
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