Magnetism and Matter
Magnetic Properties of Materials
Ferromagnetic Materials: exhibit strong magnetic properties and can be easily magnetized. Examples include iron, cobalt, and nickel
Paramagnetic Materials: Display weak magnetic properties and are weakly attracted to a magnetic field. Examples include aluminum and platinum.
Diamagnetic Materials: exhibit very weak repulsion when placed in a magnetic field. Examples include copper and bismuth.
Magnetic Field Intensity (H)
Magnetic field intensity () is a measure of the strength of a magnetic field in a material.
It is related to the magnetization () of the material by the equation , where is the magnetic flux density and is the permeability of free space.
Magnetic Susceptibility ( χ)
Magnetic susceptibility is a measure of how easily a material can be magnetized in the presence of an external magnetic field.
It is defined as , where is the magnetization and is the magnetic field intensity.
A magnetic dipole is a pair of opposite magnetic charges (north and south poles) separated by a small distance.
Magnetic dipoles are found in elementary particles and also in macroscopic objects like magnets.
Magnetic Field Lines in a Bar Magnet
Magnetic field lines emerge from the north pole and enter the south pole in a bar magnet.
The field lines form closed loops and do not intersect.
Magnetic Field Inside and Outside a Bar Magnet
Inside a magnet, the magnetic field lines run from the south pole to the north pole.
Outside the magnet, the field lines follow a north-to-south direction.
Magnetic Field due to a Magnetic Dipole
The magnetic field at a point on the axial line of a magnetic dipole is given by , where is the magnetic moment of the dipole and is the distance from the dipole.
Bar Magnet as an Equivalent Solenoid
A bar magnet can be considered as equivalent to a solenoid when viewed from a distance.
The north pole of the bar magnet corresponds to the end from which field lines emerge in the equivalent solenoid.
Torque on a Magnetic Dipole in a Uniform Magnetic Field
A magnetic dipole experiences a torque () when placed in a uniform magnetic field ().
The torque is given by , where is the magnetic moment of the dipole.
Para-, Dia-, and Ferromagnetism
Paramagnetism: Materials with unpaired electrons that align with an external magnetic field.
Diamagnetism: Materials with all paired electrons that slightly repel from an external magnetic field.
Ferromagnetism: Materials with a spontaneous alignment of magnetic dipoles, resulting in strong magnetization.
The Curie temperature is the temperature at which a ferromagnetic or ferrimagnetic material loses its magnetic properties.
Above this temperature, thermal agitation disrupts the alignment of magnetic domains.