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Introduction to Magnetism

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Presentation on theme: "Introduction to Magnetism"— Presentation transcript:

1 Introduction to Magnetism
Chapter 16

2 What is a magnet? Magnet:
Material that can create magnetic effects by itself Magnetic: The ability to exert forces on magnets or other magnetic materials

3 Types of MAGNETS Permanent Magnet: (hard magnets)
Material that keeps its magnetic properties, even when it is not close to other magnets. Example: Lodestone containing magnetite Temporary Magnet: (soft magnets) Acts as a magnet only as long as it is in the magnetic field produced by a permanent magnet or an electric current.

4 Elements that can be magnetic:
Fe: Iron soft iron loses magnetism easily Co: Cobalt used to harden tools Ni: Nickel used to make jewelry Other magnets: Compass Earth

5 Properties of magnets Have lined up atoms
Have polarity – North and South poles Cannot have only 1 pole *** magnetic poles cannot be isolated*** Like poles repel; Opposite poles attract

6 What is a magnetic Field
An area where the force exists; area where force is felt Leaves north pole & enters south pole Strongest at the poles

7 Field lines around a magnet

8 Earth’s Magnetic field
Compass: Device containing a magnet that interacts with Earth’s magnetic field to indicate direction

9 ELectromagnetism

10 Electric Current and Magnetism
In 1819, Hans Christian Oersted, a Danish physicist and chemist, and a professor, placed a compass needle near a wire through which he could make electric current flow. When the switch was closed, the compass needle moved just as if the wire were a magnet.

11 Electric Current and Magnetism
Electric current is made of moving charges (electrons), which creates the magnetic field around a current-carrying wire Magnetism is created by these moving charges

12 The magnetic fields of straight wire
The magnetic field lines are concentric circles with the wire at the center of the circles. The direction of the field depends on the direction of the current in the wire.

13 The magnetic fields of straight wire
The strength of the magnetic field near the wire depends on two factors: The strength is directly proportional to the current, so doubling the current doubles the strength of the field. The field strength is inversely proportional to the distance from the wire. (Decreasing the distance to the wire by half doubles the strength of the field.)

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