DAY 14 – 15 MAGNETISM n MAGNETIC MATERIALS
ELEMENTS of Earth’s Magnetic Field
Horizontal Component of B
Vertical Component of B
Angle of DIP or Inclination
Angle of Declination
Variation of Dip and Declination
Basics of Dia Para and Ferro magnetic substances
Their Behaviour in UNIFORM Magnetic Field
Their Behaviour in NONUNIFORM Magnetic Field
CURIE LAW
CURIE TEMPERATURE
SUPERCONDUCTOR
SUSCEPTIBILITY
PERMEABILITY
Table of Differences of these materials
Identifying material for Making Permanent or Temporary magnet
Uses of Hysteresis
NOW here so far derivations are concerned please note
The Derivation of B due to BAR MAGNET
TORQUE on BAR MAGNET
ENERGY of BAR MAGNET in magnetic field
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Diamagnetic Substance: These are feebly repelled when placed in magnetic field. They have only paired electron (No Magnetic moment of their own)
Paramagnetic: These are feebly attracted when placed in magnetic field. They have unpaired electron & hence net dipole moment of their own.
Ferromagnetic strongly attracted when in magnetic field. They have nonzero magnetic dipole moment and individual interact in such a way that their dipole moments have common directions. These groups are called domains.
| Property | Diamagnetic | Paramagnetic | Ferromagnetic |
| 1. Effect in magnetic field
2. In a uniform field 3. In a nonuniform field 4. Permeability value 5. Effect of temperature 6. Susceptibility 7. Magnetic lines than outside 8. Example |
Shows slight repulsion
Aligns perpendicular to field Tends to move from stronger to weaker parts of field μ<< 1 Diamagnetism not effected by temperature Small –ve value Slightly less than outside
Bi, Au, Cu, Hg, Sb |
Shows slight attraction
Aligns parallel to field Tends to move from weaker to stronger parts of field μ > 1 Paramagnetism decreases with temperature Small +ve value Slightly more than outside Al, Pt, Cr, Mn, CuSO4 |
Shows strong attraction
Aligns parallel to field Tends to move from weaker to stronger parts of field μ >> 1 Ferromagnetism decreases with temperature Large +ve value Much more than outside
Fe, Co, Ni |
Curie Law: state that intensity of magnetization (M) is (i) proportional to magnetic induction (B) and inversely proportional to temperature (T) in Kelvin scale. The temperature at which magnetization ceases is called Curie temperature. Most of the metals have Curie temperature much less than their melting point, also when a substance is melted it does not retain its magnetization on re-solidifying
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Hysteresis: is the phenomenon of lagging of magnetic induction (B) and intensity of magnetization (M) behind the magnetizing (H), when a specimen is taken through a cycle of magnetization.
PROPERTY OF MATERIAL FOR MAGNET
Permanent HIGH RETENTIVITY AND HIGH COERCIVITY HIGH PERMEABILITY
Electromagnet LOW RETENTIVITY and low COERCIVITY AND HIGH PERMEABILITY
Study the character when magnetic material (DIA, PARA or FERRO) is kept in magnetic field.
NOTES
NCERT
- Define neutral point. Locate the positions of neutral points when a small bar magnet is placed with its north pole: (i) towards north of the earth and (ii) towards south of the earth
- What is Gauss law in magnetism? What does it signify?
- A short bar magnet of magnetic moment 0.9 J/T−1, is placed with its axis at 45o to a uniform magnetic field. If it experiences a torque of 0.063 joule, (i) calculate the magnitude of the magnetic field and (ii) What orientation of the bar magnet corresponds to the stable equilibrium in the magnetic field?
- A short bar magnet of magnetic moment 0.9 JT−1 (joule per tesla) placed with its axis at 45o with a uniform external magnetic field experiences a torque of magnitude 0.063 J. Find the strength of the magnetic field.
- A magnetized needle is placed 30° with the direction of uniform magnetic field of intensity 3 ´ 10−2 The torque acting on the needle is 7.2 ´ 10−4 J. Calculate the magnetic moment of the needle.
- A magnetized needle of magnetic moment 4.8 ´ 10−2 JT−1 is placed at 30o with the direction of uniform magnetic field. The torque acting on the needle is 7.2 x 10−4 Calculate the magnitude of magnetic field. DAY 15: Magnetic elements and materials
- Name the elements of earth’s magnetic field at a place. Explain their meaning.
- How does the angle of dip vary as one moves from the Equator towards the North Pole? If the horizontal component of earth’s magnetic field at a place where the angle of dip is 60o is 0.4 ´ 10−4 tesla, calculate the vertical component and the resultant magnetic field of earth at that point.
- Define angle of dip at a given place. What is the value of the angle of dip on the equator?
- Define the terms magnetic inclination and horizontal component of Earth’s magnetic field at a place. Establish the relationship between the two with the help of a diagram.
- Distinguish between a diamagnetic substance and a paramagnetic substance stating two points of difference.
- How will you distinguish a diamagnetic substance from a paramagnetic substance in respect of their behaviour in a uniform and non − uniform field?
- The vertical component of earth’s magnetic field at a place is times the horizontal component. What is the value of angle of dip at this place?
- What is Curie Temperature ?
- Why is Dia behaviour independent of temperature ?