Physical Science - Chapter 18.3 Notes

This is a set for electricity from magnetism.

Discovery of Induction

Joseph Henry and Michael Faraday independently discovered induction

Faraday’s Credit

Faraday is credited because he published detailed documentation

Faraday’s Key Observation

A changing magnetic field is required to produce current

Static Magnetic Field

No current is induced when the magnetic field is not changing

Electromagnetic Induction

Producing electric current by changing a magnetic field or moving a conductor

Induced Current Direction

The current reverses when the direction of magnetic motion reverses

Increase Current by Motion

Increase the speed of relative motion between magnet and coil

Increase Current by Coil Design

Increase the number of loops in the wire coil

Generator Function

Converts mechanical energy into electrical energy

Generator Mechanism

A rotating coil moves through a magnetic field to induce current

Slip Rings

Allow current to transfer from a rotating coil to an external circuit

Transformer Function

Changes the voltage of alternating current

Why AC Works in Transformers

AC constantly changes direction creating a changing magnetic field

Primary Coil Role

Receives AC and turns the iron core into a temporary electromagnet

Magnetic Flux

The changing magnetic field produced by AC in the primary coil

Secondary Coil Role

Receives induced current from the changing magnetic flux

Step Up Transformer

Has more windings on the secondary coil to increase voltage

Step Down Transformer

Has fewer windings on the secondary coil to decrease voltage

Induction Requirement

Induction only occurs when magnetic flux is changing

Mechanical to Electrical

Generators rely on motion to create changing magnetic fields

Coil Rotation Effect

Rotating the coil changes magnetic flux and induces alternating current

Iron Core Purpose

Concentrates magnetic flux to improve induction efficiency

Faraday’s Law

Induced voltage depends on the rate of change of magnetic flux

Study Tip

If nothing is moving or changing there is no induced current