Definitions [4]
A magnet is a material that produces a magnetic field and can attract magnetic substances such as iron, nickel, cobalt, and some of their alloys.
The region around a magnet in which it can exert a magnetic force is called its magnetic field.
Magnetic Flux (ϕ): Total number of magnetic field lines passing through a given area, measured in weber (Wb).
A magnetic line of force is an imaginary curve in a magnetic field such that the tangent drawn at any point on it gives the direction of the magnetic field at that point.
Formulae [1]
Magnetic Field Strength (B): B = \[\frac {ϕ}{A}\]
where A is the area normal to the field, valid for a uniform field.
SI Unit of B: tesla (T)
Conversion: 1 T = 104 gauss
Theorems and Laws [1]
State Tangent Law in magnetism.
Tangent law states that, if a magnetic field ‘B’ is applied at right angles to the horizontal component of the earth's field BH, the needle comes to equilibrium at an angle ‘ to the magnetic meridian such that, tan θ = `B/B_H`.
Key Points
- Every ordinary magnet has two poles: north and south.
- Like poles repel; unlike poles attract.
- A freely suspended magnet aligns approximately along the north–south direction.
- Magnetic field lines are closed loops.
- A broken magnet always produces smaller magnets, each with both poles.
- Earth behaves approximately like a giant magnet.
- Near geographic north lies Earth’s magnetic-south region in the simple bar-magnet model.
- A compass works because its needle aligns with Earth’s magnetic field.
- Field lines show field direction (tangent) and strength (density)
- They form closed loops, never intersect, and are denser near poles
- Uniform field = parallel, equidistant lines
- B = ϕ/A; SI units: flux in weber, field strength in tesla
- Attraction/repulsion explained via the "contracting and laterally repelling" elastic analogy
- A bar magnet behaves like a solenoid
- Both produce similar magnetic field patterns
- Solenoid Relation: M = NIA
