State the differences between the properties of temporary magnets (made of soft iron) and the properties of permanent magnets (made of steel)

4.1 Simple phenomena of magnetism

Objective

State the differences between the properties of temporary magnets (made of soft iron) and the properties of permanent magnets (made of steel).

What are temporary magnets?

Temporary magnets are made from soft iron. They become magnetic only when exposed to a magnetic field. Once the field is removed, they lose their magnetism. Think of them as a magnetic sponge that only holds magnetism while it is being squeezed by an external field. 🔧

What are permanent magnets?

Permanent magnets are made from steel (often alloyed with cobalt, nickel or rare‑earth elements). They retain their magnetism even after the external field is removed. They are like a magnetic bookmark that stays in place on a page. 🧲

Key differences

  • Magnetisation response – Temporary: magnetises only in a field. Permanent: retains magnetisation.

  • Remanence (residual magnetisation) – Very low. High.

  • Coercivity (resistance to demagnetisation) – Low; easy to demagnetise. High; hard to demagnetise.

  • Typical use – Electromagnets, magnetic switches. Bar magnets, magnetic storage.

  • Energy requirement – Requires current to stay magnetic. No external energy needed.

Illustrative table

PropertyTemporary Magnet (Soft Iron)Permanent Magnet (Steel)
Magnetisation when exposed to fieldYes – becomes magneticYes – remains magnetic
Remanence (\$B_r\$)≈ 0 T≈ 0.5–1.5 T
Coercivity (\$H_c\$)Low (≈ 10–50 kA/m)High (≈ 200–500 kA/m)
Typical applicationElectromagnets, magnetic switchesBar magnets, magnetic storage
Energy requirementCurrent needed to stay magneticNone – retains magnetism

Quick recap with emojis

  1. 🔧 Temporary – like a sponge, needs a field to hold magnetism.

  2. 🧲 Permanent – like a bookmark, stays magnetic on its own.

  3. ⚙️ Use – temporary for switches, permanent for everyday magnets.

  4. 📚 Remember – remanence and coercivity are the key numbers that tell us how strong and stable a magnet is.

Understanding these differences helps you choose the right type of magnet for any experiment or real‑world application. Happy magnetising! 🚀