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.