Materials can be classified 3 ways

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1 Magnetism

2 Magnetism A magnet is an object that can attract other objects containing iron, cobalt, or nickel. Magnetic substances are created when electrons from within the atom or from another atom spins in the same direction this increases the magnetic field given off by the electron (each spinning electron creates its own tiny magnetic field)

3 The spinning of electrons in the same direction causes a north and south pole to form. Every magnet has at least one north pole and one south pole. If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. S N S N S N

4 Materials can be classified 3 ways Non Magnet: Will not attract a magnet or a ferromagnetic substance Glass, plastic, rubber or wood Work well as insulators for electrical wires Ferromagnet Not a magnet but something that can become magnetized by hitting, heating, or touching it with a magnet OR by adding an electrical charge (electromagnet) Is attracted by a magnet Must contain one of the following: iron, nickel or cobalt The magnetism can be turned on and off. Permanent Magnet can attract another magnet AND a ferromagnetic substance

5 Ferromagnet Magnet

6 Magnetic Fields Magnets produce magnetic forces and have magnetic field lines The magnetic force is that force of attraction or repulsion between magnets The magnetic field is the area of space in which the magnetic force can work on another magnet

7 Mapping Magnetic Fields Rules: The magnetic field lines can never cross Always flow from North to South The closer the lines, the stronger the attraction The lines near the poles are closer to one another because the poles have the greatest magnetic intensity

8 Draw in the magnetic field lines

9 Draw in the magnetic field lines

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11 Compass The needle of the compass is a small bar magnet free to turn on a pivot Red (or any color) tip of the needle is considered North and will always be attracted towards its opposite the South

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13 Because the needle of a compass is a small magnet we can use it to identify the poles of another magnets. When a compass is placed next to another magnet, the north pole of the compass will point to the south pole of the magnet (also indicating the direction of the magnetic field lines)

14 Electromagnetism straight line conductor (AKA a wire) Electricity and Magnetism how are they related? When an electric current passes through a wire a magnetic field is formed. Have a North and a South pole They have a circular magnetic field

15 Straight Line Conductor Right Hand Rule Point your thumb in the direction of conventional current (toward the negative terminal.) The direction that your fingers wraps around the wire show the direction of the magnetic field lines -- the hand may either be in front or behind, depending on where the negative post is found These lines are circular Your fingernails always point South and your knuckles point North If you place a compass near the wire, the north pole of the compass will point in the direction of your finger nails (the same direction as the arrows) South and North will be found above or below the straight line conductor NEVER at the ends

16 Because the field is circular, the direction of the compass depends on where the compass is located in relation to the wire

17 Practice I I + Current flow into the paper Current flow out the paper

18 Practice Show the direction the compass will point if placed in that position - + The direction of the compass is the same as the magnetic field lines at the same position

19 Electromagnets and Solenoids Electromagnets are solenoids with a ferromagnetic core Metal core (usually iron) wrapped with a wire (usually copper) the magnetic field comes from the electric current in the wire and the magnetization of the core This results in a very powerful magnet that can be switched on or off use the 2 nd right hand rule for solenoids The magnetic field looks like the magnetic field around a bar magnetic

20 The 2 nd right hand rule: Place palm of right hand at the positive terminal. The longer line or post is always positive. At the positive end look to see if the wire runs in front or behind the tube. Front: place hand on top and over the core (thumb points to negative terminal - where thumb points is North) Behind: place hand under the core and curl up (thumb points to positive terminal - where thumb points is North) Tip: field flow is N to S always

21 1) Start at the positive of the battery wrap your fingers the way the wires are wrapping (in the direction of conventional current 2) The direction your thumb is point is the north pole of the magnet Thumb is pointing this way S N

22 S Identify the north and south pole on the solenoid shown N

23 Try the following: N S S N

24 Increasing the strength of an electromagnet: 1. Increase current in wire 2. Increase # of loops of wire 3. Use an iron core (easily magnetized) 4. Decrease temperature To compare two solenoids with the same core, multiply the current by the number of loops the higher number is the stronger electromagnet

25 Electromagnetic Induction An electric current can produce a magnetic field, but a magnetic field can also produce electric current. Electromagnetic induction is the phenomena where an electric current can be produced by changing the magnetic field around a conductor Can be produced in two ways: By moving a magnet around a conductor By moving a conductor within a magnetic field

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