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. When you break a magnet into tiny pieces, each piece has 2 poles.

Magnetic Fields

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.

Earth’s Magnetic Field

Electric Current and its Magnetic Effect

Magnetic field using

Refer to Micah’s video.

Solenoid

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.

Magnetic field due to solenoid

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

Electric Generator