Magnetism and Matter Lect-03 (Notes).pdf

ALAKH PANDEY PHY NOTES

1. Ch-05 Magnetism & Matter Lect-03
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2. Today’s Goal
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Earth’s Magnetism
Elements of Earth’s
Magnetism
Neutral Point

3. Magnetic Needle & Nomenclature of Poles
1.When a Magnetic Needle is moved close to
Earth’s Surface, then at two places it becomes
vertical(perpendicular) to the surface.
2.The place where ‘N’ pole of needle points
vertically downward, that point on Earth’s
surface is called Magnetic North Pole.
3.The place where ‘S’ pole of needle points
vertically downward, that point on Earth’s
surface is called Magnetic South Pole.
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4. G.N: Geographical North Pole
M.N : Magnetic North Pole
G.S: Geographical South Pole
M.S: Magnetic South Pole
G.E : Geographic Equator
M.E: Magnetic Equator
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5. Angle of Dip or Magnetic Inclination(??????)
1.A magnetic needle which is free to rotate in vertical
plane (called Dip needle) is placed at various places
on Earth’s surface.
2.The needle aligns with Earth’s Magnetic Field lines
with North Pole of needle pointing towards
Magnetic North Pole.
3.At this instant , the angle made by needle with the
horizontal to Earth’s Surface is called Angle of
Dip(??????)
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6. 1.At Magnetic
Equator
2.At Magnetic
Poles
??????=??????
Needle is aligned
with horizontal
??????=????????????
�
Needle is ⏊to horizontal
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7. At any place →??????
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8. Angle of Dip or Magnetic Inclination (??????) is the angle
made by Earth’s Total Magnetic Field ??????
�????????????with the
horizontal(horizontal to ground) component of Earth’s
Magnetic Field at a point.
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9. Q 1) If the horizontal component of earth’s magnetic field at a
place where the angle of dip is 60
o
is 0.4x10
-4
T, calculate the
vertical component and the resultant magnetic field at that
place.
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10. Geographical Meridian, Magnetic Meridian
& Angle of Declination (D)
1.Geographical Meridian: At any point on Earth’s Surface, a
plane passing through Geographic Poles and that point.
2.Magnetic Meridian: At any point on Earth’s Surface, a
plane passing through Magnetic Poles and that point.
3.Angle of Declination(D): At any point on Earth’s Surface,
the angle between Geographic Meridian & Magnetic
Meridian.
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12. a)90
o
b)75
o
c)105
o
d)6
o
Q 2) The declination at a place is 15
o
west of north. In which
direction should a ship be steered with respect to compass
needle so that it reaches a place due east ?
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13. a)98
o
b)82
o
c)62
o
d)118
o
Q 3) A ship is to reach a place 10
o
south of west. In which
direction should it be steered with respect to compass needle
if the declination at the place is 18
o
west of north?
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14. a)18
o
N of East
b)72
o
N of East
c)18
o
S of East
d)72
o
S of East
Q 4) A ship is sailing due east according to Mariner’s compass.
If the declination of that place is 18
o
east of north, what is the
true direction of the ship ?
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15. Element of Earth’s Magnetism
“ The Earth’s Magnetic Field at a place can be
completely described by the three parameterswhich
are called elements of earth’s magnetic field or
elements of earth’s magnetism”
1.Angle of Declination (D)
2.Angle of Dip or Magnetic Inclination(??????)
3.Horizontal component of Earth’s Magnetism Field
(B
H)
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16. Important Note
As you can see in the image
that at most places only
Horizontal Component of
Earth’s Magnetic Field is
present & vertical component is
very small.
So, most of the time we consider only Horizontal
component (B
H) of Earth’s Magnetic Field.
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17. NEUTRAL POINT
Q) Sketch the Magnetic Field lines due to a BAR Magnet
when it is placed with its North Pole towards North Pole of
Earth.
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18. Magnet placed with its North Pole towards
North of Earth
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19. Q) Define Neutral Point.
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20. Q) Sketch the Magnetic Field Lines due to a BAR Magnet
when it is placed with its North Pole towards South Pole of
Earth.
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21. Magnet placed with its North Pole towards
South of Earth
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22. Thank You
Download lecture notes of
this lecture right after this
session .
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