Biomagnetism Flashcards
What is an electric current?
An electric current is the single direction movement of charged particles.
What are the “charged particles” in the electric current?
charged particles in metal = electrons
charged particles in the electrolyte and gas = ions
What are the types of electrical currents?
1) continuous or direct current
2) pulse current
3) alternating current
What is meant by “direct current”?
current when its amplitude is constant during time t.
What is meant by “Pulse current”?
current when its amplitude changes during time t.
What is meant by “Alternating current”?
current when the amplitude and direction changes during time t.
What is the main characteristic of an electric current?
the current density “J”.
What is a magnetic field created by?
an electric current
What is a “magnetic field”?
A magnetic field is an invisible field which exerts magnetic force on substances which are sensitive to magnetism.
What does it mean that magnetic field sources are “dipolar”?
Magnetic field sources have a north and south magnetic pole.
What are the main characteristics on which a magnetic field depends on?
a) the magnitude and direction of the current
b) the geometry of the configuration (wether the charge flows in a straight like or circle)
c) the medium which surrounds it (ie. vacuum, air, water, iron, wood)
How is the “magnetic induction” determined? What are its units?
The three factors determine a vector point.
Tesla or Gauss.
What are “magnetic field lines”?
“Magnetic field lines” give the direction in which the magnetic force acts.
When is a magnetic field considered “homogenous”?
A magnetic field is considered “homogenous” when the value and direction of vectors of the magnetic induction are all in the same point of the magnetic field.
What are the units of “magnetic field intensity”?
ampere per meter.
What is the magnetic field which surround the Earth called?
geomagnetic field
What is Amperes law about?
if a current flows in a conductor (I), and it is a homogenous magnetic field, then the force which was acting on it is directly proportional the the current strength (I), conductor length (l), magnetic induction (B).
What did Biot and Savart investigate? What law did they come up with?
a) the magnetic induction created by an electric current, is proportional to the current strength.
b) magnetic induction depends on the magnitude of a conductor carrying the electric current.
c) the magnetic induction depends on point P position in respect to the conductor.
What does Gauss’s law for magnetism state?
the magnetic field (B) has a divergence equal to zero (solenoidal vector field).
RIGHT HAND RULE
LEFT HAND RULE
What is membrane permeability?
Membrane permeability shows how many times the force of interaction in surrounding space is bigger as interaction in vacuum.
How can a magnetic field be created?
a) movement of charge
b) current flow in the conductor
How can movement of charge be established?
Electrons move in concentric circles around the nuclei.
What are magnetic materials characterised by?
Magnetization.
What are the three groups of magnetic material?
ferromagnetic, paramagnetic, diamagnetic.
What is diamagnetism?
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field.
It causes a repulsive effect.
What is the relative magnetic permeability of diamagnetic substances?
What is the magnetic susceptibility of diamagnetic substances?
relative magnetic permeability < 1.
magnetic susceptibility < 0.
less than!
What is used for diagnostics of heart disease?
magnetocardiagram (heart muscle magnetic field and current is recorded)
What is paramagnetism?
Paramagnetic material exhibits a magnetization which is proportional to the applied magnetic field in which the material is placed.
Paramagnetism is a form of magnetism which only occurs in the presence of an externally applied magnetic field.
- without a magnetic force the paramagnetic material spins are randomly orientated.
What is the relative magnetic permeability of paramagnetic substances?
What is the magnetic susceptibility of paramagnetic substances?
relative magnetic permeability > 1.
magnetic susceptibility >1.
relative magnetic permeability = a positive
magnetic susceptibility.
What is ferromagnetism?
internal magnetic field»_space; external magnetic field
Ferromagnets retain magnetized after the external field is removed.
What is the relative magnetic permeability of ferromagnetic substances?
What is the magnetic susceptibility of ferromagnetic substances?
ferromagnetic permeability is not fixed!! (dependent on temperature and external magnetic field strength.)
What does “MRI” stand for?
Magnetic Resonance Imaging
What are quantum numbers associated with?
Quantum numbers are associated with the energy states of an atom.
What are the 4 quantum numbers? What are their subscripts?
1) principal quantum number (n)
2) angular quantum number (l)
3) magnetic quantum number (m)
4) spin quantum number (s)
What does the principal quantum number describe?
The size of the orbital.
as n increases = the orbital becomes larger = electron spends more time away from the nucleus = higher potential energy of electron = electron is less tightly bound to the nucleus = energy of the orbital
What does the angular quantum number describe?
The shape of the orbital.
describes the orbital angular momentum of an electron around its nucleus.
- ranges from 0 to n-1
What does the magnetic quantum number describe? How many orientations can they have?
Describes the orientation in space of a particular orbital.
- doesn’t affect the electron’s energy, but it affects the probability cloud.
- they can have 21+1 orientations
What is space quantization?
the phenomenon that the electron orbital angular momentum vectro can have 21+! orientations which restricts the fraction of totak angular momentum.
What does the spin quantum number describe? How many orientations can they have?
describes the unique quantum state of an electron.
- can have spin up or spin down
What is the Bohr Magneton?
A physical constant of the magnetic moment of electrons.
How does the nuclear spin for individual protons and neutrons?
the nuclear spin for individual protons and neutrons parallels the treatment of electron spin (with spin 1/2 and associated magnetic movement).
What is the Zeeman effect?
The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field.
Why is the Zeeman effect important?
The Zeeman effect has multiple applications such as in:
- nuclear magnetic resonance spectroscopy
- electron spin resonance spectroscopy
- magnetic resonance imaging
What is Electron paramagnetic resonance? (EPR) What is electron spin resonance? (ESR) spectroscopy
It is a echnique for studying chemical species that have one or more unpaired electrons
eg.
- organic and inorganic free radicals
- inorganic complexes possessing a transition metal ion.
What is usually kept fixed during practice?
the frequency
What is the Lorentz force law?
- The Lorentz Force is the force on a charged particle due to electric and magnetic fields.
- A charged particle in a magnetic field will only feel a force due to the magnetic field if it is moving with a component of its velocity perpendicular to the field. If it moves parallel to the magnetic field, it experiences no force.
F=q(E+v*B)
F- force
q- change
v- velocity
B- magnetic field strength
E- external electric field
What is the principal behind MRI’s?
- a noninvasive medical imaging test that produces detailed images of almost every internal structure in the human body, including the organs, bones, muscles and blood vessels.
- The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient and sends pulses of radio waves from a scanner.
1) The strong magnetic field created by the MRI scanner causes the atoms in your body to align in the same direction.
2) Radio waves are then sent from the MRI machine and move these atoms out of the original position.
3) As the radio waves are turned off, the atoms return to their original position and send back radio signals.
–> These signals are received by a computer and converted into an image of the part of the body being examined.
–> This image appears on a viewing monitor.
