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Intro. To Magnetism. Chapter 16. Properties of a Magnet. Magnet : Material that can create magnetic effects by itself. Magnetic Material: Are affected by magnets but do not actively create their own magnetism Example: Iron or steel Permanent Magnet:
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Intro. To Magnetism Chapter 16
Properties of a Magnet • Magnet: • Material that can create magnetic effects by itself. • Magnetic Material: • Are affected by magnets but do not actively create their own magnetism • Example: Iron or steel • Permanent Magnet: • Material that keeps its magnetic properties, even when its not close to other magnetics
The Magnetic Force • All magnets have two opposite magnetic poles. • North Pole and South Pole • When near each other , magnets exert forces. • Attractive or Repulsive
The Magnetic Field • Two magnets create forces on each other at a distance much larger than the size of the magnets. • Magnetic Field: • The magnetic force that surrounds magnetic objects at all points in space. • A force field • Source Magnet: • Magnet that creates a field • Magnetic Field Lines: • Arrows used to show the direction of magnetic force in a magnetic field
Learning Check #1 • Is it possible to have a magnetic south pole without a north pole? Explain your answer. • Describe the interaction between each set of magnetic poles: two north poles; a north and south pole; two south poles. • What does the direction of magnetic field lines tell you?
Earth’s Magnetic Field • The planet Earth is one large magnet. • The source of the Earth’s magnetism is the hot, dense core composed of nickel, iron and other metals. • Huge electric currents flow in the molten iron to produce Earth’s magnetic field.
How does a Compass work? • The north pole of a magnet always points to the south pole of a permanent magnet. • Because of direction of magnetic field lines. • The north pole of a compass needle points to the Earth’s geographic north because it is a south magnetic pole. • South magnetic pole = North geographic pole • North magnetic pole = South geographic pole
Earth’s Magnetic Field • The Earth’s magnetic field is relatively weak. • Averages about 0.5 gauss at the surface. • Gauss = unit used to measure strength of magnetic field • Earth’s magnetic poles have reversed many times over the last tens of millions years. • 500,000 years on average • Last switch approximately 750,000 years ago