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Magnetism and magnetic effects of electric current — Syllabus

Tamil Nadu Board · Class 12 · Physics

What Magnetism and magnetic effects of electric current covers in Tamil Nadu Board Class 12 Physics: 4 topics, for the 2026-27 session.

45 questions31 flashcards5 formulas & key relations5 concepts

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Illustrates a current-carrying loop behaving as a magnetic dipole with North and South poles, and the direction of its magnetic moment (M) using the Right Hand Rule.
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4 Topics · Tamil Nadu Board Class 12 Physics · 2026-27

Topics in Magnetism and magnetic effects of electric current

1

Earth's Magnetic Field and Magnetic Elements

  • Earth behaves like a gigantic bar magnet with its magnetic south pole near the geographic north pole.
  • Three magnetic elements fully describe Earth's field at any point: Declination (D), Dip/Inclination (I), and Horizontal Component (B_H).
  • Declination (D): Angle between geographic meridian and magnetic meridian at a point. For Chennai: D = −1°16′ (westward).
2

Basic Properties of Magnets and Coulomb's Law of Magnetism

  • Magnetic dipole moment p_m = q_m × 2l, where q_m is pole strength and 2l is magnetic length. Direction: south to north pole.
  • Magnetic length is always less than geometrical length. Ratio = 5/6 ≈ 0.833.
  • Magnetic field B = F/q_m. Unit: N A⁻¹ m⁻¹ (or Tesla).
3

Magnetic Field Due to a Bar Magnet (Axial and Equatorial)

  • Axial line: a point on the line joining both poles of the magnet (end-on position).
  • Equatorial line: a point on the perpendicular bisector of the magnet (broad-side on position).
  • B_axial is in the direction of magnetic moment (S to N); B_equatorial is opposite to magnetic moment.
4

Torque on a Bar Magnet and Potential Energy

  • A bar magnet in uniform field experiences zero net force but a torque that tends to align it with the field.
  • Torque: τ = p_m × B sinθ (in magnitude), Vector form: τ⃗ = p⃗_m × B⃗.
  • Potential energy: U = −p_m B cosθ = −p⃗_m · B⃗ (reference: θ = 90°).

Key Concepts

The Earth's magnetic field is completelyDefined as the product of poleThe force between two magnetic polesFor a short bar magnet (rA magnetic dipole in uniform field

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Frequently Asked Questions

What are the important topics in Magnetism and magnetic effects of electric current for Tamil Nadu Board Class 12 Physics?
Key topics in Magnetism and magnetic effects of electric current include Earth's Magnetic Field and Magnetic Elements, Basic Properties of Magnets and Coulomb's Law of Magnetism, Magnetic Field Due to a Bar Magnet (Axial and Equatorial), Torque on a Bar Magnet and Potential Energy. Study these first, then practise questions on each for the Tamil Nadu Board Class 12 board exam.
How should I revise Magnetism and magnetic effects of electric current for the Tamil Nadu Board Class 12 board exam?
Learn the core ideas first, then work through the 45 practice questions on Magnetism and magnetic effects of electric current. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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All Tamil Nadu Board Class 12 Physics Syllabus

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