Topic: "Simple phenomenon of magnetism

Page 1: Introduction to Magnetism

  • Magnetism Basics

    • Defined as a physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces between objects.

  • Types of Materials

    • Magnetic: Can be magnetized.

      • Examples: Iron, Steel

    • Non-magnetic: Cannot be magnetized.

      • Examples: Plastic, Wood, Copper, Aluminium, Glass

  • Molecular Alignment

    • Magnetic materials have molecules that can align based on polarity.

    • Non-magnetic materials have molecules that cannot align.

  • Soft vs. Hard Magnetic Materials

    • Soft: Easy to magnetize/demagnetize (e.g., Iron).

    • Hard: Difficult to magnetize/demagnetize (e.g., Steel). Forms permanent magnets.

  • Electromagnets

    • Formed by soft magnetic materials.

Page 2: Methods of Magnetization and Demagnetization

  • Methods of Magnetization

    • Stroking Method:

      • Single Stroking

      • Double Stroking

    • Electrical Method:

      • Utilizes direct current (d.c) in a solenoid.

      • Right-Hand Grip Rule:

        • Thumb points to N-Pole, curled fingers follow the current direction.

  • Methods of Demagnetization

    • Heating a magnet.

    • Hammering a magnet.

    • Throwing a magnet on the floor.

    • Electrical method using alternating current (A.C).

Page 3: Induced Magnetism

  • Induced Magnetism

    • Occurs when an iron core is magnetized in the presence of a permanent magnet.

  • Magnetic Field

    • Defined as the space/region around a magnet where its magnetic effects can be felt.

    • Represented by magnetic lines of force.

  • Neutral Point

    • The point at which the magnetic forces are balanced.

Page 4: Electromagnetic Effects

  • Current-Carrying Wire in Magnetic Field

  • Electromagnets

    • Utilized in circuit breakers, electric bells, magnetic relays, and motors.

  • Force on Wire

    • Force acting on a current-carrying straight wire placed in a magnetic field.

Page 5: Fleming's Left-Hand Rule

  • Fleming's Left-Hand Rule

    • Forefinger: Magnetic Field (N to S)

    • Middle Finger: Current (I)

    • Thumb: Force (F)

  • Forces on a Rectangular Coil

    • No force on sides BC and AD as current is parallel to magnetic field.

    • Maximum force on sides AB and CD as current is perpendicular to magnetic field.

  • D.C Motor

    • Converts electrical energy into mechanical energy. Works on Fleming's Left-Hand Rule.

Page 6: Mechanical and Electrical Components of D.C Motor

  • Key Components

    • Coil, Rheostat, Carbon Brushes, Split Rings, Commutator.

  • Function of Components

    • Protect coil from excessive current.

    • Split rings reverse the current direction after each 180° rotation.

  • Factors Affecting Coil Rotation

    • Amount of current.

    • Magnetic field strength.

    • Number of wire turns in the coil.

Page 7: Electromagnetic Induction and Magnetic Flux

  • Magnetic Flux

    • Magnetic lines of force passing through a perpendicular area per unit time.

  • Faraday's Law of Electromagnetic Induction

    • Induced electromotive force (emf) in a circuit is proportional to the rate of change of magnetic flux.

  • A.C Generator

    • Converts mechanical energy into electrical energy based on Faraday's Law.

Page 8: Induced Current in A.C Generators

  • Slip Rings and Brushes

    • Transfer induced emf from coil to external circuit as induced current.

  • Magnetic Flux and Induced emf

    • Maximum flux when coil is horizontal and minimum when vertical.

  • Current Direction Determination

    • Based on Fleming's Right-Hand Rule.

Page 9: Transformers

  • A.C Transformer

    • Converts high alternating voltage to low voltage and vice versa.

  • Types of Transformers

    • Step-Up Transformer: Increases voltage (more turns in secondary coil).

    • Step-Down Transformer: Decreases voltage (fewer turns in secondary coil).

Page 10: Transformer Efficiency

  • Power Input vs. Output

    • If 100% efficient: Power input = Power output.

  • Key Formulas

    • Ns/Vs = Np/Vp

    • Current relations: Is x Vs = Ip x Vp

  • Functioning Voltage

    • A transformer always operates on alternating voltage/current.