PhysicsCBSE Class 12 · Magnetism and Matter

Diamagnetic, Paramagnetic and Ferromagnetic Substances Class 12

Updated 15 October 2026 · Fact-checked

Diamagnetic substances are weakly repelled by a magnet (χ small and negative); paramagnetic substances are weakly attracted (χ small and positive); ferromagnetic substances are strongly attracted (χ very large and positive) because their atomic moments line up in domains. Heating weakens paramagnetism and can turn a ferromagnet into a paramagnet.

Understand Diamagnetic, Paramagnetic and Ferromagnetic Substances

Hold a strong magnet near an iron nail, an aluminium foil and a copper coin. The nail jumps to the magnet, the foil is pulled very slightly, and the copper is pushed away, though too weakly to notice without careful apparatus. These are the three classes of magnetic behaviour.

Diamagnetism. In a diamagnetic substance the atoms have no permanent magnetic moment. An applied field changes the motion of the electrons slightly, inducing a small moment opposite to the field (a bit like Lenz's law at the atomic level). So:

χ is small and negative; $μ_{r}$ is slightly less than 1; M is opposite to H.
The substance moves from stronger to weaker field regions (weakly repelled by a magnet).
Field lines inside are slightly fewer than outside: the material pushes field lines out a little.
It hardly depends on temperature.
Examples: bismuth, copper, lead, silicon, water, nitrogen (at STP), sodium chloride.
A superconductor at very low temperature is a perfect diamagnet: χ = −1, $μ_{r}$ = 0, and it expels the field completely (the Meissner effect).

Paramagnetism. The atoms do have permanent magnetic moments, but they point at random because of thermal motion, so there is no net magnetisation without a field. An applied field lines them up partly:

χ is small and positive; $μ_{r}$ is slightly more than 1; M is along H.
The substance moves from weaker to stronger field regions (weakly attracted).
Field lines inside are slightly denser.
Alignment competes with thermal agitation, so the susceptibility decreases as temperature rises (and increases on cooling).
Examples: aluminium, sodium, calcium, oxygen (at STP), copper chloride.

Ferromagnetism. The atoms have permanent moments, and neighbouring moments tend to line up with each other spontaneously, forming regions called domains, each fully magnetised. In an unmagnetised piece the domains point in different directions, so the net magnetisation is small. An applied field makes domains aligned with it grow and others rotate towards it, producing a very large magnetisation:

χ is very large and positive (hundreds to thousands); $μ_{r} ≫ 1$ .
Strongly attracted; field lines crowd into the material.
Examples: iron, cobalt, nickel, gadolinium and their alloys.
Effect of temperature: heating disturbs the alignment within domains. Above a certain temperature, which depends on the material, the domain structure breaks down and the material behaves as a paramagnet.

How to tell them apart in experiments.

A rod suspended between the poles of a strong magnet: a paramagnetic or ferromagnetic rod turns to lie along the field; a diamagnetic rod turns to lie across it (so as to keep most of its length in the weaker field).
A liquid in a U-tube with one arm between the poles: a paramagnetic liquid rises in that arm; a diamagnetic liquid is lowered.
In a non-uniform field, para- and ferromagnets move towards the stronger field, diamagnets towards the weaker field.

Diamagnetic, Paramagnetic and Ferromagnetic Substances: formulas and key facts

Diamagnetic: $χ < 0 (small), μ_{r} < 1$; No permanent atomic moments; induced moment opposes the field.
Paramagnetic: $0 < χ ≪ 1, μ_{r} > 1 (slightly)$; Permanent moments, randomly oriented without a field.
Ferromagnetic: $χ ≫ 1, μ_{r} ≫ 1$; Domains of aligned moments.
Perfect diamagnet (superconductor): $χ = - 1, μ_{r} = 0, B_{in s i d e} = 0$; The Meissner effect.
Magnetisation: $M = χH, μ_{r} = 1 + χ$; Sign of χ gives the direction of M relative to H.

How to solve Diamagnetic, Paramagnetic and Ferromagnetic Substances questions

Questions on this topic are about classification, comparison and explanation. Use this checklist.

1Classify from the data: the sign and size of χ, or μ_r compared with 1, or the observed behaviour (attracted, repelled, how strongly).
2Give the atomic reason: no permanent moment (dia), random permanent moments (para), domains (ferro).
3Describe behaviour in a non-uniform field: towards stronger field (para, ferro) or weaker field (dia).
4For a suspended rod or a U-tube, use the same rule: a material that likes strong field lines up along it or rises into it.
5For temperature questions, say what heat does to alignment: weakens paramagnetism, can destroy ferromagnetism, barely affects diamagnetism.
6For numbers, use M = χH and μ_r = 1 + χ.

Diamagnetic, Paramagnetic and Ferromagnetic Substances in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Separating materials with a magnet

Suppose a recycling plant passes crushed scrap containing iron pieces, aluminium bits and copper bits under a powerful magnet that produces a strongly non-uniform field.

(a) Which material is lifted strongly, and why? (b) What does the magnet do to the aluminium and to the copper? (c) Why can't the same simple magnet separate the aluminium from the copper effectively?

Try it first, then show the solutionSolution

Iron is ferromagnetic: its domains line up with the field and it is strongly pulled towards the stronger field, so it is lifted.
Aluminium is paramagnetic: it is pulled very weakly towards the stronger field. Copper is diamagnetic: it is pushed very weakly away.
Both effects are tiny compared with gravity on the bits, so neither is lifted or moved much; a simple magnet cannot separate them.

Answer: (a) Iron, because it is ferromagnetic; (b) aluminium is attracted and copper repelled, both very weakly; (c) their responses are far too weak to beat their weight.

Memory hook: Iron jumps, aluminium leans in, copper leans away.

Effect of temperature on paramagnetism

Imagine a paramagnetic salt sample with susceptibility $3 \times 1 0^{- 4}$ at room temperature, in a field where H = $5 \times 1 0^{5}$ A/m. It is then warmed to a much higher temperature, and separately cooled in liquid nitrogen.

(a) Find its magnetisation at room temperature. (b) Predict qualitatively how the magnetisation changes on heating and on cooling, and explain. (c) Would a diamagnetic sample show the same trend?

Try it first, then show the solutionSolution

(a) $M = χH = 3 \times 1 0^{- 4} \times 5 \times 1 0^{5} = 150$ A/m.
(b) Heating increases thermal agitation, which scrambles the alignment of the atomic moments: χ and M decrease. Cooling reduces agitation, so the field lines them up better: χ and M increase.
(c) No. Diamagnetism comes from induced moments, not from aligning permanent ones, so it hardly depends on temperature.

Answer: (a) 150 A/m; (b) it falls on heating and rises on cooling; (c) no, diamagnetism is nearly independent of temperature.

Memory hook: Heat scrambles the arrows: hot paramagnets are weaker.

Tricks to remember Diamagnetic, Paramagnetic and Ferromagnetic Substances

Short memory aids. Say each one aloud once, then use it on a question the same day.

Dia = 'against'
Diamagnetic materials go against the field: negative χ, pushed to weaker field, rod sets across the field.
Use it when: Recalling diamagnetic behaviour.
Para = 'alongside', a little
Paramagnets go along with the field, but only a little: small positive χ.
Use it when: Distinguishing para from ferro.
FeCoNiGd are ferro
Iron, cobalt, nickel, gadolinium: 'Fe-Co-Ni-Gd'.
Use it when: Examples of ferromagnets.
Hot magnets get lazy
Heat weakens paramagnetism and can turn a ferromagnet into a paramagnet; diamagnets don't care.
Use it when: Effect of temperature.

Diamagnetic, Paramagnetic and Ferromagnetic Substances: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Classifying from susceptibility · 2 marks · Very short answerBoard level

Three materials have susceptibilities (i) $- 1.7 \times 1 0^{- 4}$ , (ii) $2 \times 1 0^{- 5}$ and (iii) 1999. Classify each and state its relative permeability.

Try it first, then show the solutionSolution

(i) Small negative: diamagnetic; $μ_{r} = 0.99983$ . (½)
(ii) Small positive: paramagnetic; $μ_{r} = 1.00002$ . (½)
(iii) Very large positive: ferromagnetic; $μ_{r} = 2000$ . (1)

Answer: (i) diamagnetic, 0.99983; (ii) paramagnetic, 1.00002; (iii) ferromagnetic, 2000.

Example 2: Comparing the three classes · 5 marks · Long answerBoard level

Distinguish between diamagnetic, paramagnetic and ferromagnetic substances on the basis of (a) atomic magnetic moment, (b) susceptibility, (c) behaviour in a non-uniform field and (d) effect of temperature. Give two examples of each.

Try it first, then show the solutionSolution

(a) Dia: no permanent atomic moment. Para: permanent moments, randomly oriented. Ferro: permanent moments aligned within domains. (1½)
(b) Dia: small negative. Para: small positive. Ferro: very large positive. (1)
(c) Dia: moves towards weaker field. Para: moves weakly towards stronger field. Ferro: moves strongly towards stronger field. (1)
(d) Dia: nearly independent of temperature. Para: susceptibility falls as temperature rises. Ferro: heated enough, it becomes paramagnetic. (1)
Examples: dia: bismuth, copper; para: aluminium, sodium; ferro: iron, nickel. (½)

Answer: See the comparison above: atomic moment, sign and size of χ, direction of motion in a non-uniform field and temperature dependence differ for the three classes.

Example 3: Field lines near the three materials · 3 marks · Short answerHarder board level

Describe how the magnetic field lines of a uniform field are modified when a sphere of (a) a diamagnetic, (b) a paramagnetic and (c) a ferromagnetic material is placed in it. Explain each using susceptibility.

Try it first, then show the solutionSolution

(a) Diamagnetic: lines bend slightly away; fewer lines pass through the sphere, because χ < 0 makes B inside slightly smaller than outside. (1)
(b) Paramagnetic: lines are drawn slightly into the sphere; χ > 0 (small) makes B inside slightly larger. (1)
(c) Ferromagnetic: lines crowd strongly into the sphere; χ ≫ 1 makes B inside many times larger. (1)

Answer: Dia: lines pushed out slightly; para: drawn in slightly; ferro: drawn in strongly.

Example 4: Magnetisation of three materials · 3 marks · Short answerHarder board level

(a) In a field H = $2 \times 1 0^{4}$ A/m, find the magnetisation of a paramagnet with χ = $2 \times 1 0^{- 5}$ and a diamagnet with χ = $- 1.7 \times 1 0^{- 4}$ . (b) A ferromagnetic core with μ_r = 2000 is in a solenoid with H = 200 A/m. Find M and B.

Try it first, then show the solutionSolution

(a) Para: $M = 2 \times 1 0^{- 5} \times 2 \times 1 0^{4} = 0.4$ A/m along H. Dia: $M = - 3.4$ A/m, opposite to H. (1½)
(b) $M = (μ_{r} - 1) H = 1999 \times 200 \approx 4.0 \times 1 0^{5}$ A/m. (½)
$B = μ_{r} μ_{0} H = 2000 \times 4 π \times 1 0^{- 7} \times 200 \approx 0.50$ T. (1)

Answer: (a) 0.4 A/m along H and 3.4 A/m against H; (b) M ≈ $4.0 \times 1 0^{5}$ A/m, B ≈ 0.50 T.

Example 5: Rod and U-tube tests · 5 marks · Long answerHOTS / competency

(a) A small rod of a material is suspended between the poles of a strong electromagnet. Predict how it sets itself if it is (i) bismuth, (ii) aluminium. (2)
(b) A U-tube contains a liquid, one arm placed between the poles. Predict and explain what happens to the level in that arm for a paramagnetic and a diamagnetic liquid. (2)
(c) Why are these effects hard to see with a weak magnet? (1)

Try it first, then show the solutionSolution

(a)(i) Bismuth is diamagnetic: it moves towards weaker field, so the rod turns perpendicular to the field, keeping its ends out of the strongest region. (1)
(ii) Aluminium is paramagnetic: it is drawn towards the stronger field, so the rod turns to lie along the field. (1)
(b) A paramagnetic liquid is pulled into the strong-field region, so its level rises in that arm. (1)
A diamagnetic liquid is pushed out of the strong field, so its level falls in that arm. (1)
(c) |χ| is very small (about 10⁻⁵ to 10⁻⁴), so the magnetic forces are tiny compared with weight and friction unless the field is very strong. (1)

Answer: (a) bismuth sets across the field, aluminium along it; (b) para level rises, dia level falls; (c) the forces are tiny because |χ| is small.

Example 6: A superconductor and a magnet · 4 marks · Case-basedHarder board level

Read the passage and answer.

A small magnet placed above a disc of superconducting material, cooled to a very low temperature, floats in the air above it.
(a) What type of magnetic material is the superconductor? (1)
(b) State its susceptibility and relative permeability. (1)
(c) What is the field inside the superconductor? Name the effect. (1)
(d) What would happen if the disc warmed up and stopped being superconducting (assume it is then weakly diamagnetic)? (1)

Try it first, then show the solutionSolution

(a) A perfect diamagnet. (1)
(b) χ = −1 and μ_r = 0. (1)
(c) Zero: the field is expelled completely. This is the Meissner effect. (1)
(d) Its weak diamagnetism would give only a tiny repulsion, far too small to hold up the magnet, so the magnet would fall onto the disc. (1)

Answer: (a) perfect diamagnet; (b) χ = −1, μ_r = 0; (c) zero, the Meissner effect; (d) the magnet would drop.

Where students lose marks in Diamagnetic, Paramagnetic and Ferromagnetic Substances

The slips examiners see most often, and what to write instead.

Mistake: Saying diamagnetic substances are not affected by a magnet.
The repulsion is too small to notice in everyday life.
Do this: They are weakly repelled; say 'moves from stronger to weaker field'.
Usually costs: 1 mark.
Mistake: Explaining paramagnetism with domains.
Mixing up para and ferro.
Do this: Domains belong to ferromagnets only; paramagnets have individual random moments.
Usually costs: 1 mark.
Mistake: Writing Curie's law or the hysteresis loop in an answer.
Older textbooks include them.
Do this: For 2026-27, the effect of temperature is qualitative; Curie's law and hysteresis are not in the syllabus.
Usually costs: Time, and possible errors.
Mistake: Getting the U-tube or rod direction backwards.
Forgetting which materials prefer strong field.
Do this: Para and ferro go into the strong field (rise, lie along); dia comes out (falls, lies across).
Usually costs: 1 to 2 marks.
Mistake: Listing iron oxide or steel as diamagnetic, or copper as paramagnetic.
Guessing examples.
Do this: Learn the NCERT examples for each class.
Usually costs: ½ mark per example.

Exam tips

A three-column table (dia, para, ferro) with rows for atomic moment, χ, μ_r, behaviour, temperature and examples is the clearest answer for a 3- or 5-mark comparison.
Board papers of 2023 (55/1/1 Q5 and Q16, 55/5/1 Q3) and 2024 (55/5/1 Q3) set short questions on these materials.
Draw field-line sketches (pushed out, drawn in, crowded in) when asked how the three materials modify a field.
Mention superconductors as perfect diamagnets when asked for an extreme example.
Keep temperature answers qualitative and give the reason (thermal agitation).

Practice questions on Diamagnetic, Paramagnetic and Ferromagnetic Substances

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
A substance is weakly repelled by a strong magnet. Its susceptibility is
(a) large and positive (b) small and positive (c) small and negative (d) zero
Hint
Repelled = diamagnetic.
Answer
(c) small and negative.
Q2 · 1 mark · Very short answerBoard level
Give two examples each of diamagnetic and paramagnetic substances.
Hint
Think of common metals.
Answer
Diamagnetic: bismuth, copper (also lead, water). Paramagnetic: aluminium, sodium (also calcium, oxygen at STP).
Q3 · 2 marks · Very short answerHarder board level
Explain, using domains, why an unmagnetised piece of iron is strongly attracted by a magnet.
Hint
What do domains do in an external field?
Answer
Iron consists of domains, each fully magnetised, pointing in different directions so the net magnetisation is small. In the magnet's field, domains along the field grow and others rotate towards it, giving a large magnetisation along the field. The magnetised iron is then pulled strongly towards the stronger field near the magnet.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): The susceptibility of a paramagnetic substance decreases as its temperature increases.
Reason (R): Thermal agitation disturbs the alignment of atomic magnetic moments with the applied field.
(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.
Hint
Alignment versus heat.
Answer
(a).
Q5 · 2 marks · Very short answerHarder board level
A material has relative permeability 0.99999. Find its susceptibility, classify it, and say whether it is attracted or repelled by a magnet.
Hint
χ = μ_r − 1.
Answer
χ = −1 × 10⁻⁵: diamagnetic, so it is weakly repelled (moves towards weaker field).
Q6 · 2 marks · Very short answerHOTS / competency
Why is diamagnetism present in all materials, even though it is noticed only in some?
Hint
What does a field do to every orbiting electron?
Answer
Any applied field alters the motion of electrons in every atom and induces a small moment opposing the field. In paramagnetic and ferromagnetic materials this weak effect is outweighed by the much larger alignment of permanent moments, so it is noticed only where there are no permanent moments.
Q7 · 2 marks · Very short answerHOTS / competency
A strongly heated iron nail is no longer attracted strongly by a magnet, but it is still very weakly attracted. Explain both observations.
Hint
What happens to domains at a high temperature?
Answer
Strong heating destroys the ordered alignment within domains, so the iron loses its ferromagnetism. Its atoms still have permanent moments that a field can partly align, so it behaves as a paramagnet: weakly attracted.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Sign of χ for diamagnetic substances?Show answer
Negative (small).
2.What are domains?Show answer
Regions in a ferromagnet in which all atomic moments are aligned.
3.Two ferromagnetic elements?Show answer
Iron and nickel (also cobalt, gadolinium).
4.How does a diamagnetic rod set between magnet poles?Show answer
Perpendicular to the field.
5.What happens to paramagnetic susceptibility on heating?Show answer
It decreases.
6.μ_r of a superconductor?Show answer
Zero (perfect diamagnet).

Diamagnetic, Paramagnetic and Ferromagnetic Substances: frequently asked questions

What is the main difference between paramagnetic and ferromagnetic substances?

Both have permanent atomic moments. In a paramagnet they act independently and are only slightly aligned by a field. In a ferromagnet neighbouring moments line up spontaneously in domains, so a field produces a very large magnetisation.

Why are diamagnetic substances repelled by magnets?

An applied field induces in each atom a small magnetic moment opposite to the field. The material therefore has magnetisation against the field and is pushed towards regions of weaker field.

What happens to a ferromagnet when it is heated?

Heating disturbs the alignment within its domains. Above a temperature that depends on the material, the domain alignment breaks down and it behaves like a paramagnet.

Is water magnetic?

Water is diamagnetic. It is repelled very weakly by a strong magnet, too weakly to notice in everyday life.

What is the Meissner effect?

The complete expulsion of magnetic field from a superconductor cooled below its transition temperature. It makes the superconductor a perfect diamagnet, χ = −1, which is why a magnet can float above it.