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Some animals can detect magnetic fields, whichhelps them orientate themselves and navigate. Animals which can do this include pigeons, bees, Monarch butterflies, sea turtles and certain fish.

The earth's magnetic field

In the picture below, you can see a representation of the earth's magnetic field which is very similar to the magnetic field of a giant bar magnet likethe one on the right of the picture. So the earth has two sets of north poles and south poles: geographic poles and magnetic poles .

The earth's magnetic field is thought to be caused by flowing liquid metals in the outer core which causes electric currents and a magnetic field. From the pictureyou can see that the direction of magnetic north and true north are not identical. The geographic north pole , which is the point through which the earth's rotation axis goes, is about 11,5 o away from the direction of the magnetic north pole (which is where a compass will point). However, the magnetic poles shift slightly all the time.

Another interesting thing to note is that if we think of the earth as a big bar magnet, and we know that magnetic field lines always point from north to south , then the compass tells us that what we call the magnetic north pole is actually the south pole of the bar magnet!

Interesting fact

The direction of the earth's magnetic field flips direction about once every 200 000 years! You can picture this as a bar magnet whose north and south poleperiodically switch sides. The reason for this is still not fully understood.

The importance of the magnetic field to life on earth

The earth's magnetic field is very important for humans and other animals on earth because it protects us from being bombarded (hit) by high energy charged particles which are emitted by the Sun. The stream of charged particles (mainly positively charged protons and negatively charged electrons) coming from the sun is called the solar wind. When these particles come close to the Earth, they become trapped by the Earth's magnetic field and cannot shower down to the surface where they can harm living organisms. Astronauts in space are at risk of being irradiated by the solar wind because they are outside the zones where the charged particles are trapped.

The region above Earth's atmosphere in which charged particles are affected by Earth's magnetic field is called the magnetosphere. Relatively often, in addition to the usual solar wind, the Sun may eject a large bubble of material (protons and electrons) with its own magnetic field from its outer atmosphere. Sometimes these bubbles travel towards the Earth where their magnetic fields can join with Earth's magnetic field. When this happens a huge amount of energy is released into the Earth's magnetosphere, causing a geomagnetic storm. These storms cause rapid changes in the Earth's magnetosphere which in turn may affect electric and magnetic systems on the Earth such as power grids, cellphone networks, and other electronic systems.

Aurorae (pronounced or-roar-ee)

Another effect caused by the Earth's magnetic field is the spectacular Northern and Southern Lights, which are also called the Aurora Borealis and the Aurora Australis respectively. When charged particles from the solar wind reach the Earth's magnetosphere, they spiral along the magnetic field lines towards the North and South poles. If they collide with particles in the Earth's atmosphere, they can cause red or green lights which stretch across a large part of the sky and which is called the aurora. Because this only happens close to the North and South poles, we cannot see the aurorae from South Africa. However, people living in the high Northern latitudes in Canada, Sweden, and Finland, for example, often see the Northern lights.

This simulation shows you the Earth's magnetic field and a compass.

run demo

Summary

  1. Magnets have two poles - North and South.
  2. Some substances can be easily magnetised.
  3. Like poles repel each other and unlike poles attract each other.
  4. The Earth also has a magnetic field.
  5. A compass can be used to find the magnetic north pole and help us find our direction.

This video provides a summary of the work covered in this chapter.

Khan academy video on magnets

End of chapter exercises

  1. Describe what is meant by the term magnetic field .
  2. Use words and pictures to explain why permanent magnets have a magnetic field around them. Refer to domains in your explanation.
  3. What is a magnet?
  4. What happens to the poles of a magnet if it is cut into pieces?
  5. What happens when like magnetic poles are brought close together?
  6. What happens when unlike magnetic poles are brought close together?
  7. Draw the shape of the magnetic field around a bar magnet.
  8. Explain how a compass indicates the direction of a magnetic field.
  9. Compare the magnetic field of the Earth to the magnetic field of a bar magnet using words and diagrams.
  10. Explain the difference between the geographical north pole and the magnetic north pole of the Earth.
  11. Give examples of phenomena that are affected by Earth's magnetic field.
  12. Draw a diagram showing the magnetic field around the Earth.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
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Source:  OpenStax, Physics - grade 10 [caps 2011]. OpenStax CNX. Jun 14, 2011 Download for free at http://cnx.org/content/col11298/1.3
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