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24-1 MAGNETS: PERMANENT & TEMPORARY. General Properties  Hang the bar magnet from the thread, observe what happens…….  Positions itself in the N-S directions.

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Presentation on theme: "24-1 MAGNETS: PERMANENT & TEMPORARY. General Properties  Hang the bar magnet from the thread, observe what happens…….  Positions itself in the N-S directions."— Presentation transcript:

1 24-1 MAGNETS: PERMANENT & TEMPORARY

2 General Properties  Hang the bar magnet from the thread, observe what happens…….  Positions itself in the N-S directions - magnet is polarized  Has two ends – North seeking and South seeking  A compass is a small magnet free to turn

3 General Properties  Observe what happens when another magnet is brought to the different sides of the magnet  The two N poles repel as the two S poles  N and S pole attract  All magnets have two singular poles or Monopoles  When magnet is broken in half, magnets orient themselves in a N & S direction

4 Simple Magnets  Touch a magnet to a piece of metal (iron nail) and try to pick up paper clips along the nail  Nail has become polarized (temporarily)  Either end of a magnet will attach to a metal

5 Permanent Magnets  Made of ALNICO V  Aluminum – Nickel – Cobalt – and other rare earth elements

6 Magnetic Field  Magnets are a long range force  Invisible “lines” surround the magnet showing the magnetic field  Number of magnetic lines is magnetic flux  # of lines is proportional to strength  Concentrated at the poles  Lines flow out of the N and into the S in closed loops

7 Electromagnetism  Electric currents through a wire create a magnetic field perpendicular to the current  First Right hand Rule  Direction of current  Thumb  Direction of magnetic field  Fingers coiled

8 Magnetic Field near a Coil  A wire looped several times to form a coil and a current is allowed to flow, the field around all the loops is always in the same direction  Solenoid  Long coil wire consisting of many loops

9 Magnetic Field near a Coil  When there is an electric current in a coil wire, the field acts like a permanent magnet  Electromagnet  Strength of the field is proportional to the current in the coil  Increasing the number of loops increases the strength

10 Electromagnet  Strength can also be increased by adding an iron rod inside the coil  Field will magnetize the rod  Second right hand rule  Direction of magnetic field produced by an electromagnet  Curl fingers around loops in the direction of the current  Thumb is the North pole of the magnet

11 Magnetic Domains  Each electron in an atom acts like a tiny electromagnet  generally in three magnetic elements  Iron, nickel, & cobalt  Groups of electrons are known as domains  Shown as arrows that are random in direction  Once a magnetic field is present, arrows aligned and become magnetized

12 Physics and Earth Science  Iron is found in the oceanic rocks as basalt  As ocean floor spreads, magma is released  Overtime, earth’s magnetic field has changed


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