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Magnetism and Matter Class 12 Case Based Questions 2026-27 | CBSE Physics
CBSE Class 12 Physics · Chapter 5 · 2026–27
Magnetism and Matter Class 12 Physics Case-Based Questions
8 original case-based practice sets with answers covering magnetic materials, bar magnets, field lines, magnetic dipoles, torque, magnetisation and temperature effects.
Exam-use note: These are original CBSE-style practice cases, not official board questions. The official 2026–27 Physics Sample Question Paper uses two 4-mark case-study questions in Section D, with four one-mark subparts in each case. CBSE Class XII 2026–27 SQP & Marking Scheme
1. Core Chapter 5 Case-Based Questions
These cases focus on the concepts explicitly named in the current CBSE 2026–27 Chapter 5 scope: bar magnets, equivalent solenoid, magnetic field lines, qualitative magnetic-dipole field behaviour, torque, magnetic materials, magnetisation and temperature effects. CBSE Class 12 Physics 2026–27 Curriculum
Magnetic materials · 4 marks
Case 1 — A Compass Near Different Magnetic Materials
Case: A student places small samples X, Y and Z near the pole of a strong magnet. Sample X is weakly repelled. Sample Y is weakly attracted and its induced magnetisation is in the direction of the applied field. Sample Z is strongly attracted and shows strong magnetic response. The student wants to use these observations to classify the materials.
Q1 Which sample is diamagnetic?
Answer: X is diamagnetic because diamagnetic substances are weakly repelled by a magnetic field.
Key: X
Q2 Which sample is consistent with paramagnetic behaviour?
Answer: Y is consistent with paramagnetism: it is weakly attracted and magnetises in the direction of the applied field.
Key: Y
Q3 Which sample is most likely ferromagnetic?
Answer: Z is most likely ferromagnetic because ferromagnetic substances show a much stronger magnetic response.
Key: Z
Q4 What is the usual sign of magnetic susceptibility for X?
Answer: Diamagnetic susceptibility is small and negative.
Key: Small negative χ
Bar magnet · field lines · dipole field
Case 2 — Mapping the Field of a Bar Magnet
Case: A student maps the field around a bar magnet with a small compass. At point P on the axial line and point Q on the equatorial line, both points are at the same distance from the centre of a short magnetic dipole. The student observes that the field directions are different at the two points.
Q1 What do magnetic field lines represent?
Answer: They provide a visual representation of the direction and relative strength of a magnetic field.
Key: Direction and relative strength of the field
Q2 At equal distance from a short dipole, how does the equatorial field magnitude compare with the axial field magnitude?
Answer: For a short dipole at the same distance, the equatorial field magnitude is half the axial field magnitude.
Key: B_eq = ½ B_axial
Q3 Which line is perpendicular to the magnetic axis?
Answer: The equatorial line is perpendicular to the magnetic axis through the centre of the dipole.
Key: Equatorial line
Q4 Why do field lines appear denser where the field is stronger?
Answer: Greater line density is used conventionally to represent greater magnetic field strength.
Key: Greater field-line density
Equivalent solenoid · magnetic dipole moment
Case 3 — A Current-Carrying Coil Behaves Like a Magnet
Case: A circular coil of 100 turns carries a current of 0.20 A. Its area is 2.0 × 10⁻³ m². A student compares the coil with a small bar magnet and treats the coil as an equivalent magnetic dipole.
Q1 What magnetic quantity describes the strength and orientation of a magnetic dipole?
Answer: The magnetic dipole moment describes the strength and orientation of a magnetic dipole.
Key: Magnetic dipole moment
Q2 Write the expression for the dipole moment of the coil.
Answer: For a current-carrying coil, m = NIA.
Key: m = NIA
Q3 Calculate the magnetic moment of the coil.
Answer: m = 100 × 0.20 × 2.0 × 10⁻³ = 0.040 A m².
Key: 0.040 A m²
Q4 Why can the coil be treated as an equivalent magnetic dipole in this context?
Answer: A current-carrying coil produces a magnetic field pattern that can be represented qualitatively by a magnetic dipole.
Key: Because its magnetic behaviour is dipole-like
Torque · magnetic dipole
Case 4 — A Magnetic Dipole in a Uniform Field
Case: A magnetic dipole of moment 1.5 A m² is placed in a uniform magnetic field of 0.40 T. The angle between the magnetic moment and the field is changed from 30° to 90°.
Q1 Write the expression for the torque on the dipole.
Answer: The magnitude of torque is τ = mB sin θ.
Key: τ = mB sin θ
Q2 Calculate the torque at 30°.
Answer: τ = 1.5 × 0.40 × sin30° = 0.30 N m.
Key: 0.30 N m
Q3 Calculate the torque at 90°.
Answer: τ = 1.5 × 0.40 × 1 = 0.60 N m.
Key: 0.60 N m
Q4 At what angle is the torque maximum?
Answer: Since sin θ is maximum at 90°, the torque is maximum at 90°.
Key: 90°
Magnetisation · volume
Case 5 — Measuring Magnetisation
Case: A small specimen has a magnetic dipole moment of 0.24 A m² and a volume of 3.0 × 10⁻⁴ m³. A student wants to compare the magnetisation of specimens of different sizes.
Q1 What is magnetisation?
Answer: Magnetisation is the magnetic dipole moment per unit volume of a material.
Key: Magnetic moment per unit volume
Q2 Write the expression for magnetisation.
Answer: M = m/V.
Key: M = m/V
Q3 Calculate M for the specimen.
Answer: M = 0.24/(3.0 × 10⁻⁴) = 800 A m⁻¹.
Key: 800 A m⁻¹
Q4 If the magnetic moment doubles while volume remains fixed, what happens to M?
Answer: Because M is directly proportional to magnetic moment when volume is fixed, M doubles.
Key: It doubles
Temperature effect · Curie temperature
Case 6 — Heating a Ferromagnetic Material
Case: A laboratory sample is strongly ferromagnetic at room temperature. The student gradually heats it. At a particular temperature, called the Curie temperature, the characteristic ferromagnetic ordering is lost.
Q1 What happens to ferromagnetic behaviour above the Curie temperature?
Answer: Above the Curie temperature, the material loses ferromagnetic ordering and behaves as a paramagnetic substance.
Key: It becomes paramagnetic
Q2 Why is temperature important in magnetic materials?
Answer: Temperature changes the degree of magnetic ordering and therefore changes the magnetic response of materials.
Key: It affects magnetic ordering
Q3 Which class is generally associated with strong magnetic ordering?
Answer: Ferromagnetic materials exhibit strong cooperative magnetic ordering.
Key: Ferromagnetic
Q4 Is Curie temperature a property used to distinguish a ferromagnet's temperature-dependent behaviour?
Answer: Yes. It marks the transition above which ferromagnetic behaviour is lost.
Key: Yes
2. Official-SQP-Linked Extension Cases
Why separate these? The official 2026–27 SQP includes a 2-mark alternative asking students to identify a magnetic material from relative permeability μr = 800, while the curriculum description uses qualitative treatment for the magnetic-dipole field. These extension cases therefore help students recognise assessment material without presenting every broader textbook relationship as a compulsory core item.
SQP-linked extension · magnetic materials
Case 7 — Relative Permeability: Assessment-Aware Extension
Case: A magnetic material is found to have a relative permeability μr = 800. A student uses this value to identify the type of magnetic response. This type of question is included in the official CBSE Class XII 2026–27 Physics Sample Question Paper as a 2-mark alternative in Section B.
Q1 Is μr = 800 close to unity?
Answer: No. It is much greater than 1.
Key: No
Q2 What broad magnetic class is associated with such a very large relative permeability?
Answer: A very large relative permeability is characteristic of a ferromagnetic material.
Key: Ferromagnetic
Q3 Name one characteristic of ferromagnetic materials.
Answer: They show very strong attraction and can retain magnetisation under suitable conditions.
Key: Strong magnetic response / retention of magnetisation
Q4 Why is this case separated from the core set?
Answer: Because the current curriculum wording emphasises the listed Chapter 5 scope, while the official 2026–27 SQP explicitly includes a relative-permeability question.
Key: Assessment-aware extension
SQP-linked extension · dipole field
Case 8 — Field Strength Changes with Distance
Case: A student studies the magnetic field of a short magnetic dipole. For points sufficiently far from the dipole compared with its size, the field magnitude on a specified line varies inversely with the cube of distance: B ∝ 1/r³.
Q1 If distance is doubled, by what factor does the field magnitude change?
Answer: B' = B/(2³) = B/8.
Key: One-eighth
Q2 If distance is tripled, by what factor does the field magnitude change?
Answer: B' = B/(3³) = B/27.
Key: One twenty-seventh
Q3 If the field at distance r is 8 × 10⁻⁵ T, what is it at 2r?
Answer: B(2r) = 8 × 10⁻⁵ / 8 = 1 × 10⁻⁵ T.
Key: 1 × 10⁻⁵ T
Q4 Why is this treated as an extension here?
Answer: It involves quantitative inverse-cube dipole-field scaling, whereas the current Chapter 5 syllabus wording describes the dipole-field treatment as qualitative.
Key: Because the current syllabus emphasises qualitative treatment
3. How to Solve a 4-Mark Case Study
- Read the passage once for the physical situation and again for the exact data.
- Underline the concept being tested: material type, dipole moment, torque, field line, magnetisation or temperature.
- For numerical subparts, write the relationship before substitution and keep SI units consistent.
- For conceptual subparts, answer the exact question first; do not write an unrelated textbook paragraph.
- Check every one-mark subpart separately. A correct earlier answer does not automatically carry marks to the next part.
4. Chapter 5 Study Resources
Chapter 5 Complete Notes
Chapter 5 Important Questions
Chapter 5 MCQs
Chapter 5 Numericals
CBSE 2026–27 Physics Curriculum
CBSE 2026–27 SQP & Marking Scheme
5. Case-Study Readiness Checklist
Before moving on, make sure you can:
□ classify dia-, para- and ferromagnetic substances from observations
□ explain the role of magnetic field lines
□ use m = NIA for a current-carrying coil
□ use τ = mB sin θ and identify maximum/zero torque
□ calculate magnetisation M = m/V
□ explain the effect of temperature on ferromagnetic behaviour
□ distinguish core syllabus practice from assessment-aware extension material
□ classify dia-, para- and ferromagnetic substances from observations
□ explain the role of magnetic field lines
□ use m = NIA for a current-carrying coil
□ use τ = mB sin θ and identify maximum/zero torque
□ calculate magnetisation M = m/V
□ explain the effect of temperature on ferromagnetic behaviour
□ distinguish core syllabus practice from assessment-aware extension material
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