magnetism and HIV Flashcards
Poles of a magnet
A magnet can exert a force on another nearby magnet. Magnets have two poles:
a north pole
a south pole
The magnetic force is strongest near the magnet’s poles.
the rules of magnetism
Two magnets will either attract or repel each other in the following way:
like poles (N-N or S-S) repel unlike poles (N-S or S-N) attract Magnetic forces are non-contact forces - this means that magnets affect each other without touching.
Examples of magnetic materials
Iron, steel, nickel and cobalt are magnetic materials. They are affected by magnets and are attracted to either pole of a magnet.
permanent magnets
A permanent magnet is often made from a magnetic material such as iron. A permanent magnet always causes a force on other magnets, or on magnetic materials. Key features of a permanent magnet:
it produces its own magnetic field
the magnetic field cannot be turned on and off - it is there all the time
Bar magnets and horseshoe magnets are examples of permanent magnets.
Induced magnets
Unlike a permanent magnet, an induced magnet only becomes a magnet when it is placed in a magnetic field. The induced magnetism is quickly lost when the magnet is removed from the magnetic field.
they are only attracted by other magnets, they are not repelled
they lose most or all of their magnetism when they are removed from the magnetic field
testing for magnetism
A permanent magnet can:
attract or repel another permanent magnet
attract a magnetic material (but not repel it)
This means that you can only show that an object is a permanent magnet by checking if it repels another magnet.
How to detect magnetic field
A magnetic field is invisible, but it can be detected using a magnetic compass. A compass contains a small bar magnet on a pivot so that it can rotate. The compass needle points in the direction of the Earth’s magnetic field, or the magnetic field of a magnet.
How to draw magnetic field
place the plotting compass near the magnet on a piece of paper
mark the direction the compass needle points
move the plotting compass to many different positions in the magnetic field, marking the needle direction each time
join the points to show the field lines
How to interpret magnetic field drawing
the magnetic field lines never cross each other
the closer the lines, the stronger the magnetic field
the lines have arrowheads to show the direction of the force exerted by a magnetic north pole
the arrowheads point from the north pole of the magnet to its south pole
What is the test for a permanent magnet?
Repulsion is the test for a magnet. Induced magnets will only be attracted to another magnet, they will not repel.
What is charge measured in
Coulombs
What charges attract and repel
unlike charges attract and like charges repel
charging a body involves the addition of removal of
Electrons
What happens to the electrons when two insulators are rubbed together,
electrons move from one to the other and they become charged
If a positively charged rod is brought close to the
disc on top of the electroscope, what is attracted to the top of the disc
electrons
