What is Magnetism??? Hmmm…. Magnetism – A force of attraction and repulsion.

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    15-Dec-2015

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What is Magnetism??? Hmmm Slide 2 Magnetism A force of attraction and repulsion Slide 3 What Are the Properties of Magnets? Magnets have three main properties Magnets attract iron and materials that contain iron. Magnets attract or repel other magnets. One end of a magnet always points North when allowed to swing freely. Slide 4 How do Magnetic Poles Interact Each end of a magnet is called a magnetic pole. Magnetic poles that are alike repel each other Magnetic poles that are unlike attract each other The magnetic effect is strongest at the poles Slide 5 Magnetic Force the attraction or repulsion between magnetic poles. Produced when magnetic poles come near each other and interact. Any material that exerts a magnetic force is a magnet. Slide 6 Magnetic Fields The area of magnetic force around a magnet is known as its magnetic field Magnetic field lines map out the invisible magnetic field around a magnet. Spread out from one pole Curve around the magnet Return to the other pole Slide 7 Magnetic Fields Lines form complete loops and never cross Always leave the North Pole and enter the South Pole The closer the lines are the stronger the field Strong Magnetic Field Weak Magnetic Field Slide 8 Single Magnetic Field Although you cannot see a magnetic field, you can see its effects. The magnetic forces of the magnet act on the iron filings and align them along the invisible magnetic field lines. Slide 9 Combined Magnetic Field The magnetic field of two or more magnets overlaps The effects of magnetic force on iron filings when the poles of two magnets are brought near each other. The fields from unlike poles attract each other, forming a strong field between the magnets. Slide 10 Combined Magnetic Field The fields from two like poles repel each other Slide 11 Slide 12 Compass A compass is a device that has a magnet on a needle that spins freely; it is used for navigation because its needle usually points north. Slide 13 Earths Magnetic Field The motion of Earths iron outer core creates a magnetic field similar to a bar magnets magnetic field. Slide 14 Electric Charge The interaction between electric charges is called electricity. An electric field is a region around a charged object where the objects electric force is exerted on other charged objects. When electric charges are made to flow through a material, they produce an electric current. An electric motor is a device that uses an electric current to turn an axle. An electric motor transforms electrical energy into mechanical energy. Slide 15 Electromagnetic Force Electromagnetism the relationship between electricity and magnetism. An electric current produces a magnetic field. When there is no current in the wire, the compass needles all point north When current is present, the compass needles align with the magnetic field produced by the current in the wire. Slide 16 Magnetic Fields Produced by a Current The magnetic field produced by a current has strength and direction. The field can be turned on or off By turning the electric current on or off The field can have its direction reversed By reversing the direction of the current The field can have its strength changed By increasing the amount of current or by making a loop or coil in the wire. Slide 17 Solenoids and Electromagnets - use electric current and coiled wires to produce strong magnetic fields A coil of wire with a current is called a solenoid. The two ends of a solenoid act like the poles of a magnet, but the north and south pole change when the direction of the current changes. Slide 18 A solenoid with a ferromagnetic core is called an electromagnet Magnetic field of an electromagnet is MUCH stronger that the magnetic field of a solenoid Slide 19 There are four ways to make an electromagnet stronger 1.Increase the current in the solenoid 2.Add more loops of wire to the solenoid 3.Wind the coils of the solenoid more closely together 4.Use a material that is more magnetic than iron. Example: Alnicol

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