Biomagnetism

Question 1

What is an electric current?

Answer 1

An electric current is the single direction movement of charged particles.

Question 2

What are the “charged particles” in the electric current?

Answer 2

charged particles in metal = electrons
charged particles in the electrolyte and gas = ions

Question 3

What are the types of electrical currents?

Answer 3

1) continuous or direct current
2) pulse current
3) alternating current

Question 4

What is meant by “direct current”?

Answer 4

current when its amplitude is constant during time t.

Question 5

What is meant by “Pulse current”?

Answer 5

current when its amplitude changes during time t.

Question 6

What is meant by “Alternating current”?

Answer 6

current when the amplitude and direction changes during time t.

Question 7

What is the main characteristic of an electric current?

Answer 7

the current density “J”.

Question 8

What is a magnetic field created by?

Answer 8

an electric current

Question 9

What is a “magnetic field”?

Answer 9

A magnetic field is an invisible field which exerts magnetic force on substances which are sensitive to magnetism.

Question 10

What does it mean that magnetic field sources are “dipolar”?

Answer 10

Magnetic field sources have a north and south magnetic pole.

Question 11

What are the main characteristics on which a magnetic field depends on?

Answer 11

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)

Question 12

How is the “magnetic induction” determined? What are its units?

Answer 12

The three factors determine a vector point.
Tesla or Gauss.

Question 13

What are “magnetic field lines”?

Answer 13

“Magnetic field lines” give the direction in which the magnetic force acts.

Question 14

When is a magnetic field considered “homogenous”?

Answer 14

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.

Question 15

What are the units of “magnetic field intensity”?

Answer 15

ampere per meter.

Question 16

What is the magnetic field which surround the Earth called?

Answer 16

geomagnetic field

Question 17

What is Amperes law about?

Answer 17

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).

Question 18

What did Biot and Savart investigate? What law did they come up with?

Answer 18

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.

Question 19

What does Gauss’s law for magnetism state?

Answer 19

the magnetic field (B) has a divergence equal to zero (solenoidal vector field).

Question 20

RIGHT HAND RULE

Question 21

LEFT HAND RULE

Question 22

What is membrane permeability?

Answer 22

Membrane permeability shows how many times the force of interaction in surrounding space is bigger as interaction in vacuum.

Question 23

How can a magnetic field be created?

Answer 23

a) movement of charge
b) current flow in the conductor

Question 24

How can movement of charge be established?

Answer 24

Electrons move in concentric circles around the nuclei.

Question 25

What are magnetic materials characterised by?

Answer 25

Magnetization.

Question 26

What are the three groups of magnetic material?

Answer 26

ferromagnetic, paramagnetic, diamagnetic.

Question 27

What is diamagnetism?

Answer 27

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.

Question 28

What is the relative magnetic permeability of diamagnetic substances?
What is the magnetic susceptibility of diamagnetic substances?

Answer 28

relative magnetic permeability < 1.
magnetic susceptibility < 0.

less than!

Question 29

What is used for diagnostics of heart disease?

Answer 29

magnetocardiagram (heart muscle magnetic field and current is recorded)

Question 30

What is paramagnetism?

Answer 30

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.

Question 31

What is the relative magnetic permeability of paramagnetic substances?
What is the magnetic susceptibility of paramagnetic substances?

Answer 31

relative magnetic permeability > 1.
magnetic susceptibility >1.

relative magnetic permeability = a positive
magnetic susceptibility.

Question 32

What is ferromagnetism?

Answer 32

internal magnetic field&raquo_space; external magnetic field
Ferromagnets retain magnetized after the external field is removed.

Question 33

What is the relative magnetic permeability of ferromagnetic substances?
What is the magnetic susceptibility of ferromagnetic substances?

Answer 33

ferromagnetic permeability is not fixed!! (dependent on temperature and external magnetic field strength.)

Question 34

What does “MRI” stand for?

Answer 34

Magnetic Resonance Imaging

Question 35

What are quantum numbers associated with?

Answer 35

Quantum numbers are associated with the energy states of an atom.

Question 36

What are the 4 quantum numbers? What are their subscripts?

Answer 36

1) principal quantum number (n)
2) angular quantum number (l)
3) magnetic quantum number (m)
4) spin quantum number (s)

Question 37

What does the principal quantum number describe?

Answer 37

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

Question 38

What does the angular quantum number describe?

Answer 38

The shape of the orbital.
describes the orbital angular momentum of an electron around its nucleus.
- ranges from 0 to n-1

Question 39

What does the magnetic quantum number describe? How many orientations can they have?

Answer 39

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

Question 40

What is space quantization?

Answer 40

the phenomenon that the electron orbital angular momentum vectro can have 21+! orientations which restricts the fraction of totak angular momentum.

Question 41

What does the spin quantum number describe? How many orientations can they have?

Answer 41

describes the unique quantum state of an electron.
- can have spin up or spin down

Question 42

What is the Bohr Magneton?

Answer 42

A physical constant of the magnetic moment of electrons.

Question 43

How does the nuclear spin for individual protons and neutrons?

Answer 43

the nuclear spin for individual protons and neutrons parallels the treatment of electron spin (with spin 1/2 and associated magnetic movement).

Question 45

What is the Zeeman effect?

Answer 45

The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field.

Question 46

Why is the Zeeman effect important?

Answer 46

The Zeeman effect has multiple applications such as in:
- nuclear magnetic resonance spectroscopy
- electron spin resonance spectroscopy
- magnetic resonance imaging

Question 47

What is Electron paramagnetic resonance? (EPR) What is electron spin resonance? (ESR) spectroscopy

Answer 47

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.

Question 48

What is usually kept fixed during practice?

Answer 48

the frequency

Question 49

What is the Lorentz force law?

Answer 49

• 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

Question 50

What is the principal behind MRI’s?

Answer 50

• 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.