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Physics > 11) Magbetic Field and Properties of Tissues > Flashcards

11) Magbetic Field and Properties of Tissues Flashcards

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1
Q

Magnetic field

A

It’s generated by moving electrical charges

Any electric current causes a magnetic field

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2
Q

Magnetic induction

A

Magnetic induction B is the vector describing the direction and magnitude of the magnetic field

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3
Q

Graphic representation of magnetic field

A

The magnitude of the field line is proportional to the density of the field line

Magnetic field lines are closed loops

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4
Q

Direction of magnetic induction

A

Pointing the right hand thumb in the direction of the moving positive charge and the rest of the fingers in the direction of the magnetic field

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5
Q

Magnitude of the magnetic induction

A

dB= u_o/4 pi x IdL/r^2 x sinø

Current is I
r is the distance
U_o is free space

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6
Q

Lorentz force

A

Acts on charges moving in a magnetic field

Depends on magnitude of induction B
Magnitude Q
Velocity V

F=qvBsinø

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7
Q

Work of magnetic force

A

Magnetic force can do no work as it is perpendicular to the direction of movement

It’s not conservative

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8
Q

Movement of charged particles in a magnetic field

A

The Lorentz force acts as a centripetal force

The particle performs circular motion

DAWING

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9
Q

Application examples

A

The radius of circle depends the mass, velocity, charge

It’s used to control movement of charges particles in electron microscopy and mass spectrometers

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10
Q

Forces between current carrying wires

A

Current carrying wires interact with each other by magnetic force

Any current carrying wire includes a magnetic field

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11
Q

Ampere’s force law

A

The interaction force between 2 current elements is

dF= u_o (IdL)(I2dL2)/4pi r^2 sinø1sinø2

2 parallel wires attract each other if their currents flow in the same direction

Current is measured in amps

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12
Q

Magnetic dipole moment of a current loop

A

Direction is determined by the right hand grip rule

Magnitude is P_m=IS

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13
Q

Torque on magnetic dipole

A

In external magnetic fields a couple is generated

Magnetic moment aligns with the field lines

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14
Q

Orbital magnetic moment Of electron

A

Electron with

Charge e
Velocity v
Radius r

P_mo=1/2evr

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15
Q

Spin magnetic moment of the electron

A

P_ms=h/4pi e/m

h is planks constant
e and m is the charge and mass of the electron

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16
Q

Magnetic properties of matter

A

Determined by orbital and spin magnetic moments of the electron

The net magnetic moment of an atom is the vectorial sum of the orbital and spin magnetic moment of its electrons

17
Q

Diamagnetic materials

A

Examples
Water
Co2
Nitrogen

They have no magnetic field of their own

18
Q

Diamagnetic effect

A

Induction of a magnetic field inside the material in opposition of an externally applied magnetic field

19
Q

Diamagnetic in a magnetic field

A

The diamagnetic field inside the body is weaker than the external field

Magnets exert a repulsive force of diamagnetic bodies

20
Q

Paramagnetic materials

A

Examples

Aluminium
Liquid oxygen
Free radicals

They have no magnetic field of their own as the magnetic moments cancel out

21
Q

Paramagnetic effect

A

Generation on magnetic field inside the material in the direction of an externally applied magnetic field

22
Q

Paramagnetic in a magnetic field

A

The paramagnetic inside the material is stronger than the external

The magnets exert an attraction force on the paramagnetic body

23
Q

Ferromagnetic materials

A

Examples
Iron
Cobalt
Nickel

They are paramagnetic substances consisting of numerous magnetic domains. Above a certain temp the domains are destroyed and become ordinary paramagnetic materials

24
Q

Ferromagnetic effect

A

The internal magnetic field becomes much stronger than the external

External magnetic field aligns the magnetic domains

25
Q

Magnetic hysteresis

A

The internal magnetic field changes and takes different paths when external field is decreased or increased

26
Q

Applications of ferromagnetic

A

Used for the generation of string magnetic fields

Extraction of ferromagnetic particles out of the eye

27
Q

Magnetic properties of biological tissue

A

Most biological tissues have diamagnetic properties

The human body contains some paramagnetic atoms molecules ions and radicals

Ferromagnetic material in the body is negligible

28
Q

Effect of magnetic field on the human body

A

Mechanical vibrations of nerve and muscle fibres

Magnetohydrodynamics slows down blood flow

29
Q

Magnetocardiography

A

Non contact method for investigation of the heart

Physics (11 decks)

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