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Difficulty: MediumMagnetism Fundamentals

Soft iron is commonly used for the cores of temporary electromagnets because it combines high magnetic permeability with high retentivity.

Answer: Answer

Answer

False. Soft iron has high permeability but low retentivity.
The statement is false because soft iron has high permeability but low retentivity. High permeability allows soft iron to readily channel magnetic flux when current flows through the coil, while low retentivity ensures that the core demagnetizes rapidly as soon as current flow stops.

Step-by-Step Solution

1
Identify the operational requirements of a temporary electromagnet core.
A temporary electromagnet core must concentrate magnetic flux easily when energized and release its magnetism immediately when power is cut.
Devices like relays and solenoids must switch on and off rapidly without residual magnetism holding the mechanism closed.
2
Analyze the magnetic properties of soft iron.
Soft iron possesses high permeability (high ease of magnetization) and low retentivity (minimal residual magnetism).
Retentivity measures the ability of a material to retain magnetism after the magnetizing force is removed; high retentivity is a property of permanent magnets (such as hard steel), not temporary cores.
3
Evaluate the truth value of the statement.
The statement incorrectly claims soft iron has high retentivity, making the overall statement false.
Because soft iron has low retentivity, the claim is inaccurate.

Key Concept

Magnetic permeability and retentivity in ferromagnetic materials
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Topics

Magnetism Fundamentals

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