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G) Generator Principle - Electromagnetic Induction

 

 

 

1831 - Michael Faraday discovered that current and voltage can be induced when a conductor (closed loop) moves within a magnetic field.

Engraving by John Cochran (1821-1865) of a portrait of Michael Faraday
 in his late thirties, painted by Henry Pickersgill (1782 - 1875)
This image (or other media file) is in the public domain
because its copyright has expired.

Induced Current

© Copyright 1997, Sergey Kiselev
and Tanya Yanovsky-Kiselev

Generator

http://www.walter-fendt.de/ph11e/generator_e.htm
 
© Walter Fendt, May 8, 1998

(Note: 3 dimensional view)

Wire is perpendicular to page 

If this wire is moved up or down (perpendicular to the field), maximum current (and V) will be generated.

 

 

Moved left or right (parallel to the field), no current will be generated

 

 

 

 

Toward which point should the wire be moved to induce the maximum electric potential? (voltage)

 

 

 

 

 

Point 1, perpendicular to field

 

 

 

 

The wire movement determines
 the direction of the current

School Blocks Youtube? Use file below.

WireInMagField.mov

This movie is part of the collection: Prelinger Archives
Audio/Visual: silent, b&w

Creative Commons license: Public Domain

 

 

How to find the direction of current
 - Third Left Hand Rule

 

 

Step 1:  flux lines - Out of N into S

Step 2: 4 fingers follow flux lines

Step 3: Thumb follows movement of wire (Given)

Step 4: Palm shows Push on electrons - The current direction

 


Ex) If the wire in the picture below is moved upward, which way will the electrons flow?

Into the page OR Out of the page?

 

 

 

Out of Page

 

 

 

 

Wire moved right,
Direction of induced current?

 

 

Down

 

 

List 3 factors that determine the amount of current generated when a magnet is moved is moved through closed coil of wire

St. Mary's H.S. YouTube Channel

 

 

(V) Induced voltage - also called EMF - Electromotive Force


V  =  Blv

 

B - Magnetic Field Strength

l - length of conductor (in meters)

v - velocity of conductor moving through the field

 

 

 

 

 

Ex) Describe the direction in which the wire could be moved to produce the maximum potential difference across its ends, R and S.

Magnetic

field

directed

into the page

 

 

To the left or right

(perpendicular to field)

 

 

 

 

Lenz's Law

St. Mary's Physics Youtube Channel

School Blocks Youtube? Use file below.

Lenz's Law - St. Mary's Physics

 

 

 

 

Lenzís Law - The magnetic field around induced current opposes the wire motion that produced it.

Another way to demonstrate Lenz's Law


Use a magnetic marble (Amazon)
and an aluminum rail (Home Depot)

 

 

 

SMUPhysics
November 14, 2008


All the left hand rules only work when moving charges are negative.

 

 

What do you do when
moving charge is positive?

 

 

 

 

Right Hand Rule!

 

 

 

Magnetism

1st Left Hand Rule

2nd Left hand Rule

3rd Left Hand Rule

Left Hand Rule Game

Electron in Magnetic Field

Electron in Magnetic Field II

 

 

 

Video

 

 

 

Waves

 

Enrichment

 

Physics of Credit Cards

 

Lenz's Law

MIT Tech TV

LenzsLawMIT.mov

 

 

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