PHYS-12-ELECTROMAGNETIC-INDUCTION

Lesson Overview

  • Lesson 9.1 focuses on Electromagnetic Induction and its applications.

  • General Physics 2 is related to Science, Technology, Engineering, and Mathematics (STEM).

History of Electromagnetic Induction

  • Hans Christian Oersted's experiment: The initial investigation into the relationship between magnets and electricity.

  • Michael Faraday's further experiments (2 years later):

    • Sought ways in which a magnetic field can generate electric current.

    • Conducted experiments in the Thames River and at Waterloo Bridge to explore electricity induction from saltwater movement through Earth's magnetic field.

Applications of Electromagnetic Induction

  • Foundational work for:

    • Magneto-hydrodynamic power generation: Converts fluid kinetic energy into electrical energy through electromagnetic induction.

    • Used in everyday technologies: Generators, transformers, and magnetic stripes in IDs and ATM cards.

Understanding Electromagnetic Induction

  • Definition: Process where an electromotive force (emf) is generated in a conductor by changing the magnetic field around it.

  • Learning Competency: Identify factors influencing the magnitude and direction of induced emf and current, referring to Faraday’s Law.

Learning Objectives

  • Understand and explain electromagnetic induction.

  • Determine conditions necessary for inducing electromotive force and current.

  • Explore daily life applications of electromagnetic induction.

Faraday's Law

  • Mathematical Explanation:

    • A changing magnetic flux induces emf in a circuit.

  • Induction Experiments Overview:

    • Involves a solenoid and a magnet.

    • No current observed when the magnet is stationary.

    • Moving the magnet generates induced current (induced emf).

Observations from Electromagnetic Induction Experiments

  1. Zero current (B = 0): No magnetic field leads to no current.

  2. Current flow (B increases): Current temporarily flows when the electromagnet is activated.

  3. Current returns to zero: As magnetic field decreases.

  4. Coil area change: Compressing/decompressing induced current.

  5. Movement of solenoid: Induces current through motion within the magnetic field.

  6. Turns in coil: Increasing/decreasing turns causes variation in induced current.

  7. Turning off a magnet: Produces temporary current in the opposite direction.

  8. Rate of action: Faster actions yield greater induced current.

  9. Factors affecting emf: Geometry and magnetic fields influence induced current; composition of the material does not.

Summary of Key Concepts

  • Changing Magnetic Flux (ΦB): Causes a change in magnetic field over time, directly related to induced emf.

  • Generators and Dynamos: Convert various energy types into electrical energy.

  • Generator Components:

    • Rotor: Coiling wires around metal cores.

    • Stator: Contains plates connected to the axle, works to induce current flow.

    • Electromotive Force (emf): Generated through the rotation of the shaft and coil.

Transformers and Eddy Currents

  • Transformers: Allow long-distance electricity transmission; operate on the principle of induction.

    • Adjusts voltage and current based on the Law of Induction.

    • Uses coils of varying loops for magnetic flux transfer between coils.

  • Eddy Currents (Foucault's current): Induced electrical loops in response to changing magnetic fields.

    • Whirling motion of electrons occurs at right angles to the magnetic field.

    • Practical use in braking systems, such as train brakes.

Magnetic Card Stripes

  • Functionality: Store encoded information through magnetized layers.

  • Induction Mechanism: Swiping a card changes magnetic flux, inducing an emf in the reader.

Conclusion: Applications of Electromagnetic Induction

  • Relevant across many devices: Generators, transformers, eddy currents, and magnetic card stripes.

  • Mastery of electromagnetic induction principles essential for understanding various technological applications.