Lecture Notes: Electromagnetism by Hans Christian Oersted

Introduction to Electromagnetism

• Supported by Prudential
• Date: April 21, 1820
• Key Demonstration:
  • Hans Christian Oersted observed a compass needle moving due to electric current.
  • Discovered the connection between electricity and magnetism.
• Impact:
  • Changed the field of physics.
  • Explains modern technology like hydroelectric dams and smartphones.
  • Earth’s magnetic field protects against solar radiation.

Basics of Magnetism

• Properties of Magnets:
  • North and south poles.
  • Like poles repel; opposite poles attract.
  • Certain materials (iron, cobalt, nickel) can be magnets or are attracted to magnets.
• Earth's Magnetic Field:
  • Compass aligns with Earth's magnetic field.
  • Magnetic field lines represent the magnetic force, moving from north to south.
  • Magnetic fields can't be isolated unlike electric fields.
  • Magnetic field lines form closed loops.
• Measurement:
  • Measured in teslas (1 Tesla = 1 Newton per Ampere-meter).

Oersted's Experiment

• When a wire carries current:
  • It produces a magnetic field.
  • The magnetic field surrounds the wire in circles.
  • Direction of field lines depends on the direction of current.
• First Right-Hand Rule:
  • Thumb points in the direction of current.
  • Fingers curl in the direction of magnetic field lines.

Interaction Between Magnetic Fields and Currents

• Magnetic fields exert forces on currents and vice versa.
• Second Right-Hand Rule:
  • Arm points in the direction of current.
  • Fingers show direction of magnetic field.
  • Thumb indicates the force on the wire.
• Force Equation:
  • Magnitude of force = I * l * B * sin(θ)
  • Factors: current (I), wire length (l), magnetic field strength (B), angle (θ).*

Protection from Solar Radiation

• Earth's magnetic field deflects solar radiation.
• Force on Charged Particles:
  • Similar equation to current, but for a single charge.
  • F = qvBsin(θ)
  • Depends on charge (q), velocity (v), magnetic field (B), angle (θ).
• Third Right-Hand Rule:
  • Hand direction indicates force on a charge.
  • Force direction varies with particle charge.

Conclusion

• Oersted connected electricity and magnetism.
• Inspired further studies and experiments in physics.
• Additional Notes on Retirement Savings:
  • Suggests saving more for better retirement.
  • Example: Saving 1% more could grow savings significantly at retirement.
• Credits:
  • Crash Course Physics produced with PBS Digital Studios.
  • Filmed in Doctor Cheryl C. Kinney Crash Course Studio.