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Magnetism and Electromagnetism. Chapter 19. The Nature of Magnetism. magnetism - the force of attraction or repulsion of magnetic materials magnetic pole - the ends of a magnetic object, where the magnetic force is strongest. North and south poles
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Magnetism and Electromagnetism Chapter 19
The Nature of Magnetism • magnetism - the force of attraction or repulsion of magnetic materials • magnetic pole - the ends of a magnetic object, where the magnetic force is strongest. • North and south poles • Magnetic poles that are alike repel each other and magnetic poles that are unlike attract each other • What happens when you break a magnet? Chapter 19
Magnetic Field • The region around a magnet where the magnetic force is exerted • magnetic field lines - Diagram pg.615 • magnetic field interactions - Diagram pg.616 Chapter 19
In a magnetized material, all or most of the domains are arranged in the same direction pg.617 • making magnets - metallic object in a strong magnetic field, or rub it with a strong magnet • destroying magnets - drop it or strike it, heat it up Chapter 19
Magnetic Earth • compass - a device with a magnetized needle that can spin freely • Earth has an immense magnetic field surrounding it, just as there is a magnetic field around a bar magnet • magnetic declination - the angle between geographic north and the north to which a compass needle points pg. 624 Chapter 19
Magnetic Earth (con’t.) • Earth’s magnetic field affects the movements of electrically charged particles in space. Charged particles also affect the Earth’s magnetic field. • Molten rocks that harden can also indicate the direction of the earth’s magnetic field at the time the rocks cooled Chapter 19
Electric Current and Magnetic Fields • electric charge - a property of electrons and protons • electrons carry a negative charge • protons carry a positive charge • electric current - the flow of a charge through a material • an electric current produces a magnetic field Chapter 19
Electric circuit • A complete path though which electric charges can flow • Circuit must have: • 1) source of electrical energy, • 2) devices run by electrical energy, • 3) conducting wires and a switch Chapter 19
conductor - electric currents move freely • insulator - electric current does not flow easily, electrons bound tightly to their atoms • resistance - the opposition to the movement of electrical charges flowing through a material • superconductors - material that has no electrical resistance Chapter 19
Electromagnets • solenoid - a current carrying coil of wire with many loops that acts as a magnet • electromagnet - a solenoid with a ferromagnetic core that forms a magnet that can be turned on and off • increasing strength of electromagnet - increase current, increase number of loops of wire • recorders - vibrations of voice are changed into electric current, recorded as change in magnetic field. Create magnetic pattern. Chapter 19