87. MRI: MAGNETISM AND ELECTROMAGNETISM

Question 1

1. Define: Magnetic Predisposition of a Substance.

Answer 1

• it is the ability of external magnetic fields
• to affect the nuclei of a particular atom

Question 2

2. What is Magnetic Predisposition related to?

Answer 2

• it is related to the Electron Configurations of the
  specific atom

Question 3

3. What can be said about the state of a nucleus if it is surrounded by paired electrons?

Answer 3

• the nucleus is protected
• the nucleus is much less affected

Question 4

4. What can be said about the state of a nucleus if it is surrounded by unpaired electrons?

Answer 4

• the nucleus is not as protected
• this means that the external magnetic fields can
  significantly affect it

Question 5

5. What are the 3 types of Magnetic Predisposition?

Answer 5

1. Paramagnetism
2. Diamagnetism
3. Ferromagnetism

Question 6

6. What do Paramagnetic substances contain?

Answer 6

• they contain unpaired electrons
• these are found within the atom

Question 7

7. Define: Magnetic Moment.

Answer 7

• this is the small magnetic field that surrounds the atom
• this atom contains unpaired electrons

Question 8

8. What happens to these Magnetic Moments when there is no external magnetic field present?

Answer 8

• they will occur in a random pattern
• they will cancel each other out

Question 9

9. What happens to the Magnetic Moments of Paramagnetic Substances when an external magnetic field is present?

Answer 9

• they will align with the direction of the field
• the magnetic moments will add together

Question 10

10. How do paramagnetic substances affect External Magnetic fields?

Answer 10

• they affect them in a positive way
• they cause a local increase in the magnetic field

Question 11

11. What is an example of a Paramagnetic Substance?

Answer 11

• Molecular O

Question 12

12. What does this image show?

Answer 12

• a Homogenous Magnetic Field

Question 13

13. What does this image show?

Answer 13

• a Paramagnetic Substance

Question 14

14. What does this image show?

Answer 14

• a Paramagnetic substance in a Magnetic Field

STRONGER FORCES ARE PRESENT:
- when the lines of the magnetic field are attracted to
one another

Question 15

15. What do Diamagnetic Substances contain?

Answer 15

• they contain paired electrons
• these electrons are found within the atom

Question 16

16. What happens to the Diamagnetic Substances when there is no external magnetic field present?

Answer 16

• the Diamagnetic Substances show no net magnetic
  moment

Question 17

17. What happens to the Diamagnetic Substances when an external magnetic field is applied?

Answer 17

• the diamagnetic substances show a small Magnetic
  Moment
• the moment opposes the applied field

SUBSTANCES LIKE THIS:
- are repelled by the Magnetic Field

Question 18

18. What are some examples of Diamagnetic Substances?

Answer 18

• Water
• Fat
• Calcium
• most Biological Tissue

Question 19

19. What does this image show?

Answer 19

• this is a Homogenous Magnetic Field

Question 20

20. What does this image show?

Answer 20

• this is a Diamagnetic Substance

Question 21

21. What does this image show?

Answer 21

• this is a Diamagnetic Substance in the magnetic field

Question 22

22. Define a Ferromagnetic Substance.

Answer 22

• these are metals that are noticeably attracted to a
  magnet

Question 23

23. What happens when a Ferromagnetic Substance comes into contact with a Magnetic Field?

Answer 23

• there is strong attraction
• there is alignment within the Ferromagnetic Substance
• the Ferromagnetic substance travels in the same
  direction as the force applied

Question 24

24. What does a Ferromagnetic Substance look like when there is no magnetic field applied?

Answer 24

Question 25

25. What does a Ferromagnetic Substance look like when a Magnetic Field is applied to it?

Answer 25

Question 26

26. What happens to a Ferromagnetic Substance when the Magnetic Field has been removed?

Answer 26

FERROMAGNETIC SUBSTANCES:
- retain their magnetisation
- they remain magnetic
- they are permanently magnetised
- they become permanent magnets

Question 27

27. What can we see in this image?

Answer 27

• this is a Ferromagnetic Substance in the magnetic field

Question 28

28. What is an example of a Ferromagnetic Substance?

Answer 28

• Iron

Question 29

29. What can be said about the polarity of magnets?

Answer 29

• they are Bipolar
• they have two poles
• a North pole and a South Pole

Question 30

30. What happens when a Magnetic Field is exerted by a Magnet?

Answer 30

• it produces Magnetic Field lines
• these are also known as Lines of Force
• they run from the magnetic North pole to the Magnetic
  South Pole
• lines that run in this direction are known as Magnetic
  Lines of Flux

Question 31

31. What is the Magnetic Flux Density?

Answer 31

• it is the number of Magnetic Flux lines per unit area

Question 32

32. Which 3 units is the strength of the Magnetic Field measured in?

Answer 32

1. Gauss (G)
2. Kilogauss (kG)
   - Gauss x 1 000
3. Tesla (T)
   - Kilogauss x 10 000

Question 33

33. What happens if two magnets are brought closer together?

Answer 33

• there are forces of attraction and repulsion between
  them

Question 34

34. What does the force of attraction or repulsion depend on?

Answer 34

• the orientation of the magnetic poles relative to one
  another

Question 35

35. What happens when we put like poles next to one another?

Answer 35

• they will repel each other

IN THIS IMAGE:
- the space around the magnet consists of Magnetic
Field lines

Question 36

36. What happens when we put opposite poles next to one another?

Answer 36

• they will attract each other

IN THIS IMAGE:
- the space around the magnet consists of Magnetic
Field lines

Question 37

37. Read through this summary.
    Does everything make sense?

Answer 37

• yes