Magnetism
Temporary Magnets
Permanent magnets
Retains their magnetic properties for a long time
Made from iron, cobalt, nickel
By Sidharth Nair
Retains their magnetic properties for a short time
All magnets have two poles. North Pole and a South Pole. The names derive from the behavior of a magnet on Earth.
The magnetic forces are strongest near the ends, or magnetic poles of the magnets.
Like poles repel Unlike poles attract
Electrons as magnets
Magnetic Fields
The lines of flux travel through the magnet and leave the magnet at the north pole.
There is a magnetic field surrounding a magnet.
Every spinning electron is a tiny magnet. A pair of electrons spinning in the same direction makes up a stronger magnet.
A pair of electrons spinning in opposite directions, however, work against one another. This causes their electric fields to cancel out, making them no longer magnets.
A magnetic field can be created with moving charges, such as a current-carrying wire.
The magnetic field is proportional to the current in the wire.
The shape of the magnetic field is revealed by magnetic field lines which spread out from one pole, curve around the magnet, and return to the other pole.
Types of materials
Paramagnetic
Ferromagnetic
Diamagnetic
Materials that are weakly repelled by magnets. Many common materials are diamagnetic: water, glass, copper, graphite, salt, lead, and many plastics.
Materials that are weakly attracted to magnets. Examples: aluminum, oxygen, and uranium
Strongly attracted to magnets
Direction of the field is from North to South
Symbol is B
The earth as a magnet
The most common unit for the magnetic field is the Tesla (T). Other units such as Gauss (G) and Weber (Wb) can be used.
The equation for the force exerted on a moving charge by a magnetic field is: Fb=qvbsin(x)
A magnetic field does no work on a moving charged particle.
On a magnetic field diagram, the . corresponds to out of the page and x corresponds to in the page.
The earth has a magnetic field of its own.
The Earth’s magnetic field has reversed several times over the past million years.
Right hand rule
Fingers- Magnetic Field(B)
Palm of the Hand-Force(F)
Thumb- Direction of the velocity(v)
Magnetic Force
F=Bqv
1 Gauss = 10^-4 Tesla
The right hand rule can be used to do these types of problems with current carrying wires/coils
A solenoid is a long, helically wound coil of insulated wire.
Solenoids are also known as electromagnets
Electromagnets
changes electrical energy to mechanical energy
3 ways to increase strength
Increasing the number of coils
Increasing the current
Placing an iron Core inside the coils
Examples of electromagnets are Doorbells and Junk Yards
F = IBL sin(x)