# 0.8 Magnetism  (Page 3/4)

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As the activity shows, one can map the magnetic field of a magnet by placing it underneath a piece of paper and sprinklingiron filings on top. The iron filings line themselves up parallel to the magnetic field.

## Investigation : field around a pair of bar magnets

Take two bar magnets and place them a short distance apart such that they are repellingeach other. Place a sheet of white paper over the bar magnets and sprinkle some iron filings onto the paper. Give the paper a shaketo evenly distribute the iron filings. In your workbook, draw both the bar magnets and the pattern formed by the iron filings. Repeatthe procedure for two bar magnets attracting each other and draw what the pattern looks like for this situation. Make a note of theshape of the lines formed by the iron filings, as well as their size and their direction for both arrangements of the bar magnet.What does the pattern look like when you place both bar magnets side by side?

As already said, opposite poles of a magnet attract each other and bringing them together causes their magnetic field lines to converge (come together). Like poles of a magnet repel each other and bringing them together causes their magnetic field lines to diverge (bend out from each other).

## Ferromagnetism and retentivity

Ferromagnetism is a phenomenon shown by materials like iron, nickel or cobalt.These materials can form permanent magnets. They always magnetise so as to be attracted to a magnet, no matter whichmagnetic pole is brought toward the unmagnetised iron/nickel/cobalt.

The ability of a ferromagnetic material to retain its magnetisation after an external field is removed is called its retentivity .

Paramagnetic materials are materials like aluminium or platinum, which become magnetised in an externalmagnetic field in a similar way to ferromagnetic materials. However, they lose their magnetism when the external magnetic field is removed.

Diamagnetism is shown by materials like copper or bismuth, which become magnetised in a magnetic field with a polarity opposite to the external magnetic field. Unlike iron, they are slightly repelled by a magnet.

## The compass and the earth's magnetic field

A compass is an instrument which is used to find the direction of a magneticfield. A compass consists of a small metal needle which is magnetised itself and which is free to turn in any direction.Therefore, when in the presence of a magnetic field, the needle is able to line up in the same direction as the field.

## Interesting fact

Lodestone, a magnetised form of iron-oxide, was found to orientate itself in a north-south direction if left free to rotate by suspensionon a string or on a float in water. Lodestone was therefore used as an early navigational compass.

Compasses are mainly used in navigation to find direction on the earth. This works becausethe earth itself has a magnetic field which is similar to that of a bar magnet (see the picture below). The compass needle aligns with the earth's magnetic fielddirection and points north-south. Once you know where north is, you can figure out any other direction. A picture of a compass is shown below:

where we get a research paper on Nano chemistry....?
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
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