Magnetic Fields

Introduction

• Magnetic fields are a fundamental aspect of physics, commonly encountered in various contexts.

Visualising Magnetic Fields

• Magnetic fields are often visualised using iron filings or represented as lines with arrows indicating the direction of the field.
• Magnetic field lines typically go from the north pole to the south pole of a magnet.

Creation of Magnetic Fields

• Magnetic fields are generated by moving charges, such as electrons in a wire, which create circular magnetic fields around them.

Direction of Magnetic Fields

• The left-hand grip rule is used to determine the direction of magnetic fields when considering the motion of electrons.
  • Thumb points in the direction of electron motion (vertically upward).
  • Fingers curl in the direction of the circular magnetic field lines (horizontally).
• For positive charges or conventional current (+ to -), the right-hand grip rule can be used.

Force on Current-Carrying Wires

• When a current-carrying wire is placed in a stationary magnetic field, it experiences a force due to the interaction between the field produced by the wire's current and the stationary magnetic field.
• The force is perpendicular to the direction of movement and the stationary field lines.
• This principle is utilised in electric motors.

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Magnetic Fields

Electric Generators

• When a conductor is moved through a stationary magnetic field, it induces a current in the conductor.
• This phenomenon forms the basis of electric generators, which convert mechanical energy into electrical energy.

Fleming's Right-Hand Rule

• To determine the direction of induced current in electric generators, Fleming's Right-Hand Rule can be applied:
  • Thumb (motion) points in the direction of the wire's movement.
  • First finger (field) points in the direction of the magnetic field.
  • Second finger (current) points in the direction of the induced current, perpendicular to the first finger.

Applications

• Magnetic fields are prevalent in various technologies and devices, including electric motors, generators, transformers, and particle accelerators.

Summary

• Magnetic fields are visualised using iron filings or represented as lines with arrows.
• They are generated by moving charges and have circular patterns around current-carrying wires.
• The direction of magnetic fields can be determined using the left-hand grip rule.
• Magnetic fields exert forces on current-carrying wires, and this principle is utilised in electric motors.
• Moving conductors through magnetic fields induces current, a principle employed in electric generators.
• Fleming's Right-Hand Rule helps determine the direction of the induced current.
• Magnetic fields find applications in various technological devices and particle accelerators.