Presentation on theme: "The metals affected by magnetism consist of tiny regions called 'Domains' which behave like tiny magnets."— Presentation transcript:
The metals affected by magnetism consist of tiny regions called 'Domains' which behave like tiny magnets.
Magnetic fields Magnetic fields are areas around a magnet where there is a magnetic force. You can investigate these using a plotting compass or iron filings. Like poles repel and unlike poles attract.
Unlike poles attract. North and South. Like poles repel. North and north. South and south
Field lines run from North to South. The magnetic field is strongest at the poles.
The Earth itself has a huge magnetic field - as if it had a huge bar magnet embedded at its centre. The Earth’s magnetic field lines emerge from near the geographical north pole and re-enter it at the south pole.
Angle of Declination Difference between true north and magnetic north
Dip Angle Needle points down. Why? Shape of the world magnetic field
Now show them our compasses
Final Pattern Notice field moves from north to south
Oersted’s Experiment Hans Christian Oersted discovered in 1820 that an electric current near a compass causes the compass needle to be deflected. Oersted's experiment showed that every electric current has a magnetic field surrounding it. Hans Christian Oersted (1777-1851)
Electromagnets A wire with a current in it has a magnetic field around it. The strength of a magnetic field can be increased by wrapping a wire around an iron bar
Electromagnet A soft iron rod has no magnetic field When current flows in the wire the soft iron becomes magnetised so a magnetic field is detected by the plotting compasses.
Notice the compasses point at right angles to the current
The Earth’s magnetic field extends far into space. It is called the “magnetosphere.” When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called… The solar wind is constantly bombarding the Earth’s magnetic field. Sometimes these charged particles penetrate that field. These particles are found in two large regions known as the Van Allen Belts.
The Aurora Borealis in the Northern Hemisphere And the Aurora Australis in the Southern Hemisphere When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called…