Magnetic Materials: Comparative study of Dia-, Para-, and Ferro-magnetic substances with examples

📌 1. Question Description

🧲 Magnetic Materials

Magnetic materials are substances that show a response when placed in an external magnetic field. Depending upon the nature and strength of their response, magnetic substances are mainly classified as:

• Diamagnetic substances
• Paramagnetic substances
• Ferromagnetic substances

⭐ The main difference is based on the magnetic moment of atoms and the way these atomic magnetic moments behave in an external magnetic field.

🧠 2. Basic Magnetic Behaviour

When a material is placed in an external magnetic field, its atoms or molecules may respond differently.

🔵 Diamagnetic

Weakly repelled by a magnetic field. Their magnetic susceptibility is negative.

🟢 Paramagnetic

Weakly attracted by a magnetic field. They generally contain unpaired electrons.

🔴 Ferromagnetic

Strongly attracted by a magnetic field and can retain magnetisation.

🔵 3. Diamagnetic Substances

Diamagnetic substances are weakly repelled by an external magnetic field.

• All electrons are paired.
• Net permanent magnetic moment is approximately zero.
• Magnetic susceptibility is small and negative.
• They move from stronger magnetic field toward weaker magnetic field.
• They do not retain magnetisation after removal of the field.

χ < 0

Examples: Bismuth, Copper, Silver, Gold, Water, Mercury.

🟢 4. Paramagnetic Substances

Paramagnetic substances are weakly attracted by an external magnetic field.

• They contain one or more unpaired electrons.
• They possess a small net magnetic moment.
• Magnetic susceptibility is small and positive.
• They are attracted toward the stronger magnetic field.
• Magnetisation disappears when the external field is removed.

χ > 0

Examples: Aluminium, Platinum, Oxygen, Chromium salts, Mn salts.

🔴 5. Ferromagnetic Substances

Ferromagnetic substances are strongly attracted by an external magnetic field and can retain magnetisation even after the external field is removed.

• Strong magnetic attraction.
• Very large positive magnetic susceptibility.
• Atomic magnetic moments tend to align parallel.
• They form magnetic domains.
• They can be permanently magnetised.

χ ≫ 0

Examples: Iron (Fe), Cobalt (Co), Nickel (Ni) and some alloys.

🧩 6. Magnetic Domains in Ferromagnetic Materials

A ferromagnetic material consists of small regions called magnetic domains. Within an individual domain, atomic magnetic moments are aligned approximately in the same direction.

In an unmagnetised specimen, different domains point in different directions. When an external magnetic field is applied, many domains become aligned in the direction of the field.

🔬 7. Animated Practical — Magnetic Behaviour

Select Material Diamagnetic Paramagnetic Ferromagnetic

Magnetic Field Strength 5

Diamagnetic — Weak Repulsion

Magnetic Susceptibility: Negative

Magnetic Response: Weak Repulsion

Electron Configuration: Paired Electrons

🧪 8. Practical / Demonstration

Experiment: Comparison of Magnetic Materials

Apparatus:

• Strong permanent magnet
• Iron piece
• Aluminium piece
• Copper/Bismuth piece
• Thread or balance

Procedure:

1. Place each material separately near a strong magnet.
2. Observe the attraction or repulsion.
3. Compare the strength of magnetic response.
4. Remove the magnet and check whether magnetisation remains.

✔ Iron shows strong attraction and can retain magnetisation.
✔ Aluminium shows weak attraction.
✔ Copper/Bismuth shows weak repulsion.

📊 9. Comparative Study

Property	Diamagnetic	Paramagnetic	Ferromagnetic
Magnetic response	Weak repulsion	Weak attraction	Strong attraction
Electrons	All paired	Unpaired electrons	Unpaired moments align
Magnetic susceptibility	Small negative	Small positive	Very large positive
Magnetic moment	Nearly zero	Non-zero	Strong collective moment
Magnetisation retained?	No	No	Yes, often
Domains	No ferromagnetic domains	No ferromagnetic domains	Present
Examples	Bi, Cu, Ag	Al, Pt, O₂	Fe, Co, Ni

📝 10. MCQ Practice — 12 Questions

1. Diamagnetic substances are:

A. Strongly attracted

B. Weakly attracted

C. Weakly repelled

D. Permanently magnetised

✔ Answer: C

2. Paramagnetic substances contain:

A. Only paired electrons

B. One or more unpaired electrons

C. No electrons

D. Only neutrons

✔ Answer: B

3. Which is a ferromagnetic substance?

A. Copper

B. Bismuth

C. Iron

D. Water

✔ Answer: C

4. Magnetic susceptibility of a diamagnetic substance is:

A. Large positive

B. Small positive

C. Small negative

D. Infinite

✔ Answer: C

5. Which substance is paramagnetic?

A. Aluminium

B. Copper

C. Bismuth

D. Gold

✔ Answer: A

6. Ferromagnetism is mainly associated with:

A. Random molecular motion

B. Alignment of magnetic moments

C. Absence of electrons

D. Zero magnetic field

✔ Answer: B

7. Which material can be permanently magnetised?

A. Diamagnetic

B. Paramagnetic

C. Ferromagnetic

D. None

✔ Answer: C

8. Which has negative magnetic susceptibility?

A. Diamagnetic

B. Paramagnetic

C. Ferromagnetic

D. All

✔ Answer: A

9. Which of the following is diamagnetic?

A. Fe

B. Ni

C. Co

D. Cu

✔ Answer: D

10. Which of the following is NOT ferromagnetic?

A. Iron

B. Cobalt

C. Nickel

D. Aluminium

✔ Answer: D

11. Magnetic domains are characteristic of:

A. Ferromagnetic materials

B. Purely diamagnetic materials

C. Vacuum

D. Electrolytes

✔ Answer: A

12. Paramagnetic substances are attracted towards:

A. Weaker magnetic field

B. Stronger magnetic field

C. No field

D. Electric field only

✔ Answer: B

🟣 11. Assertion–Reason — 5 Questions

Options:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.

Assertion: Diamagnetic substances are weakly repelled by a magnetic field.

Reason: They have no permanent magnetic dipole moment in the absence of an external magnetic field.

Answer: A

Assertion: Paramagnetic substances are weakly attracted by a magnetic field.

Reason: They contain unpaired electrons.

Answer: A

Assertion: Ferromagnetic substances can retain magnetisation.

Reason: Their magnetic domains can remain aligned even after removal of the external field.

Answer: A

Assertion: Diamagnetic susceptibility is positive.

Reason: Diamagnetic substances are weakly repelled by an external field.

Answer: D

Assertion: Paramagnetic substances lose their magnetisation when the external magnetic field is removed.

Reason: Thermal motion prevents permanent alignment of their atomic magnetic moments.

Answer: A

🟢 12. 2 Marks — 6 Questions

Q1 Define diamagnetic substances and give two examples.

Q2 Define paramagnetic substances and give two examples.

Q3 Define ferromagnetic substances and give two examples.

Q4 What is magnetic susceptibility? State its sign for diamagnetic substances.

Q5 Why are paramagnetic substances attracted by a magnetic field?

Q6 What are magnetic domains?

🟡 13. 3 Marks — 6 Questions

Q1 Explain diamagnetic substances with two examples.

Q2 Explain paramagnetic substances with two examples.

Q3 Explain ferromagnetic substances and their important properties.

Q4 Differentiate between diamagnetic and paramagnetic substances.

Q5 Why do ferromagnetic substances show strong magnetic behaviour?

Q6 Explain the role of unpaired electrons in paramagnetism.

🟠 14. 4 Marks — 6 Questions

Q1 Compare diamagnetic and paramagnetic substances on the basis of electron configuration, susceptibility and magnetic response.

Q2 Compare paramagnetic and ferromagnetic substances.

Q3 Explain magnetic domains and their alignment in ferromagnetic substances.

Q4 Explain why diamagnetic substances are repelled by a magnetic field.

Q5 Explain why paramagnetic substances are attracted by a magnetic field.

Q6 Prepare a comparative table of dia-, para- and ferromagnetic substances.

🔴 15. 5 Marks — 6 Questions

Q1 Explain diamagnetic, paramagnetic and ferromagnetic substances with examples and important properties.

Q2 Give a detailed comparison between dia-, para- and ferromagnetic materials.

Q3 Explain the origin of paramagnetism in terms of unpaired electrons.

Q4 Explain the domain theory of ferromagnetism.

Q5 Explain magnetic susceptibility and compare its value for the three types of magnetic substances.

Q6 Discuss the behaviour of magnetic materials in an external magnetic field.

🔵 16. 6 Marks — 6 Questions

Q1 Give a detailed comparative study of diamagnetic, paramagnetic and ferromagnetic substances with suitable examples.

Q2 Explain the origin of magnetism in materials and classify them into diamagnetic, paramagnetic and ferromagnetic substances.

Q3 Explain the domain theory of ferromagnetism with a neat diagram and describe the process of magnetisation.

Q4 Discuss the effect of electron pairing and unpaired electrons on the magnetic properties of substances.

Q5 Explain the differences among dia-, para- and ferromagnetic materials on the basis of magnetic susceptibility, magnetic moment, attraction, domains and retention of magnetisation.

Q6 Describe the magnetic behaviour of Fe, Al and Cu and explain why these substances belong to different magnetic categories.

⚙️ 17. Applications

🧲 Ferromagnetic

• Permanent magnets
• Electric motors
• Generators
• Transformers
• Magnetic storage

⚡ Paramagnetic

• Magnetic sensors
• Oxygen detection
• Scientific instruments

🔬 Diamagnetic

• Magnetic levitation demonstrations
• Material characterization
• Scientific experiments

🚀 18. Quick Revision

🔵 Diamagnetic

Weakly repelled.

All electrons paired.

χ < 0

Examples: Bi, Cu, Ag.

🟢 Paramagnetic

Weakly attracted.

Unpaired electrons present.

χ > 0

Examples: Al, Pt, O₂.

🔴 Ferromagnetic

Strongly attracted.

Magnetic domains present.

Very large positive χ.

Examples: Fe, Co, Ni.

📚 19. Concept Sheet

Diamagnetic: Weak repulsion + paired electrons + negative susceptibility.

Paramagnetic: Weak attraction + unpaired electrons + positive susceptibility.

Ferromagnetic: Strong attraction + domain alignment + permanent magnetisation possible.

Order of magnetic response: Diamagnetic < Paramagnetic < Ferromagnetic

Important examples: Cu → Diamagnetic
Al → Paramagnetic
Fe → Ferromagnetic