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Chapter 23: Magnetism. Magnetism. Magnets are natural Lodestones called magnetites. Properties of a magnet. 1. like poles ____________, unlike poles ______________. 2. the _________ of a magnet are the strongest. The __________ of a magnet is neutral.
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Properties of a magnet • 1. like poles ____________, unlike poles ______________. • 2. the _________ of a magnet are the strongest. The __________ of a magnet is neutral. • When you break a magnet into tiny pieces, each piece has 2 poles.
The magnetic field lines continue inside the magnet to form closed loops. • When the magnetic field lines are closer → magnetic field ___________.
Demo • Materials: plain paper; two bar magnets; compass. • Aim: to draw the magnetic fields of magnets. • Procedure: • Using the given compass, draw the magnetic field of a horizontal bar magnet. • Draw the magnetic field of two magnets placed horizontally but with opposite poles facing each other. • Draw the magnetic field of two magnets placed horizontally but with like poles facing each other.
Domains of a magnet • The spinning and orbiting electrons make each atom into a tiny magnet. • In unmagnetized object, the magnetic domains point in random directions. As a result, the magnetic fields of all the domains cancel each other. • In a magnetized object, the magnetic fields of the domains are not canceled but aligned with one another. • The domains act like miniature bar magnets pointing in the N-S direction. The arrows points towards the North.
A material that shows strong magnetism is called a _________________ material. Eg: iron; nickel and cobalt, steel. • Non-magnetic materials : copper, tin.
Solenoid • solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. • Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets.
How to increase the strength of an electromagnet? • 1. increase the current. • 2. add more loops • 3. loops closer together • 4. stronger ferromagnetic material. eg: increase the size of the material.
Electric Motor converts electrical energy to kinetic energy. • Fleming’s Left Hand Rule
Electromagnetic Induction • Current is produced when a close loop conductor cuts through the magnetic field. • Fleming’s right hand rule