MAGNETIC FIELD & MAGNETIZATION – COMPLETE NOTES
1. Magnetic Field Induction (Magnetic Flux Density)
Symbol: B SI Unit: Tesla (T) In Free Space: B = μ₀H
2. Magnetic Field Due to Current Carrying Conductors
(A) Long Straight Wire
B = μ₀I / (2πR) ; I = Current, R = Distance from wire
(B) Centre of a Circular Coil
B = μ₀NI / (2R) ; N = Number of turns, R = Radius B ∝ N
(C) Inside a Long Solenoid
B = μ₀NI / L ;N = Number of turns, L = Length of solenoid
3. Uses of Current Carrying Conductors
• Electric Motor • Generator • Fan Not used in Heater (heater works on heating effect, not magnetic effect)
4. Magnetic Field Intensity
Also called Magnetic Field Strength or Magnetizing Field Symbol: H Unit: A/m
5. Magnetization
M = Magnetic Dipole Moment / Volume ; Unit: A/m
6. Relation Between B, H and M
B = μ₀ (H + M)
χ = M / H
B = μ₀ (1 + χ) H
χ = Magnetic Susceptibility (Dimensionless)
7. Force on Moving Charge in Magnetic Field
F = q (v × B)
Magnitude: F = qvB sinθ
8. Radius of Circular Motion in Magnetic Field
r = mv / (qB)
• An electric heater converts electrical energy into heat energy using resistive heating elements.
• An electric motor works on the principle of the Lorentz force acting on a current-carrying conductor in a magnetic field.
• An electric generator operates on electromagnetic induction, producing EMF when a conductor moves in a magnetic field.
• An electric fan uses an electric motor to convert electrical energy into mechanical energy to rotate blades.
• The pattern of the magnetic field around a conductor depends on the shape of the conductor.
• An electromagnet produces a magnetic field when electric current passes through it.
• Electromagnets convert electrical energy into magnetic energy.
• A current-carrying conductor generates a magnetic field around it and behaves like a magnet.
• Moving charges perpendicular to a magnetic field experience the Lorentz force.
• In a long solenoid, the magnetic field inside is uniform, parallel to its axis, and strong.
• The magnetic field outside a solenoid is weak and non-uniform.
• Magnetic field lines around a straight current-carrying conductor form concentric circles.
• A solenoid is a coil of many closely wound circular turns of insulated copper wire in cylindrical form.
• A charged particle moving perpendicular to a magnetic field experiences a force determined by the right-hand rule.
• The Right-Hand Thumb Rule is used to determine the direction of the magnetic field around a current-carrying conductor.
• Magnetic field lines show the direction and strength of the magnetic field around a magnet.
• Magnetic field lines emerge from the north pole and enter the south pole of a magnet.
• Magnetic field lines form closed loops, indicating the absence of magnetic monopoles.
• Magnetic field lines are absent in regions where the magnetic field strength is zero.
• Introducing a soft iron core inside a solenoid increases the magnetic field strength.
• Soft iron enhances magnetic field strength due to its high magnetic permeability.