Electromagnetism Lecture Notes

Introduction to Electromagnetism

• Phenomenon where electric currents produce magnetic fields
• Explored within wires, coils, solenoids, and electromagnets

Magnetic Field around a Wire

• Current flowing through a wire generates a magnetic field
• Field lines are concentric circles around the wire
  • Closest near the wire (strongest magnetic field)
• Right Hand Rule:
  • Thumb in the direction of current
  • Fingers curl in the direction of the magnetic field
• Example: Current upwards -> Magnetic field anti-clockwise

Opposite Direction Current

• Magnetic field direction depends on current direction
• Use right hand rule (upside down for opposite direction) to determine

Magnetic Field in a Circular Coil

• Joining wires to form a flat circular coil
• Current flows through, magnetic fields interact and stretch out
• Fields form ellipses; combine into a single magnetic field through coil center

Solenoids

• Multiple turns of wire create a solenoid
• Properties:
  • Strong and uniform magnetic field within
  • Similar to a bar magnet outside
  • North and South poles defined by field lines
• Solenoid = Electromagnet (electricity creates a magnet)
• Electromagnets:
  • Magnetic only with current
  • Magnetic field disappears when power is off
  • Field direction can be reversed by reversing current

Increasing Electromagnet Strength

1. Increase the current through the solenoid
2. Increase the number of turns in the coil
3. Decrease the length of the coil (keeping turns constant)
4. Add an iron core inside the solenoid

• Iron core is a soft magnetic material
  • Becomes an induced magnet when current flows
  • Massively increases strength of the electromagnet
  • Loses its magnetic properties when current is off

Conclusion

• Electromagnets are versatile with adjustable strength and polarity
• Useful for various applications

End of Lecture

• Hope you enjoyed today's session!