This document provides information about electromagnetism and magnetic fields produced by electric currents. It discusses Hans Christian Oersted's experiment in 1820 that discovered a current-carrying conductor produces a magnetic field. It then describes the magnetic fields produced by straight and circular current-carrying conductors. Additional topics covered include the right-hand rule, electromagnets, solenoids, and applications such as the electric bell. Diagrams illustrate many of the concepts and experimental setups.

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Electromagnetism

2. Electromagnetism
Dr. Pius Augustine, SH College, Kochi

3. Hans Christian Oersted 1777 - 1851 (Denmark)
Dr. Pius Augustine, SH College, Kochi

4. Oersted’s experiment
Current flowing through a wire
produces magnetic field around it
A B

5. Dr. Pius Augustine, SH College, Kochi

6. Dr. Pius Augustine, SH College, Kochi

7. What is the shape of
magnetic field lines around a
straight current carrying
conductor ?
Concentric circles
Dr. Pius Augustine, SH College, Kochi

8. What is the shape of magnetic
field lines around a circular
current carrying conductor ?
Concentric lines around the two
ends of the conductor and
straight lines at the centre of the
conductor. Dr. Pius Augustine, SH College, Kochi

9. A wire AB connected to a battery
Current flows from A to B
Place compass needle just
below it.
On pressing the key, compass is
deflected. Dr. Pius Augustine, SH College, Kochi

10. Direction of deflection of
compass depends on
relative position of the
conductor w.r.to compass
and direction of current.
Dr. Pius Augustine, SH College, Kochi

11. Conclusions of Oersted’s experiment
i. Current carrying conductor
behaves like a magnet.
ii. Strength of B is a function
of current.
Dr. Pius Augustine, SH College, Kochi

12. Conclusions of Oersted’s experiment
i. B is at right angles to the
direction of flow of current .
ii. Deflection of needle depends
on relative position of
conductor w.r.to needle.
Dr. Pius Augustine, SH College, Kochi

13. Change in electric field produces magnetic field
Dr. Pius Augustine, SH College, Kochi

14. Direction of deflection - SNOW rule
Current flows from south to north
over a magnetic needle, then its
north pole turns towards west.
Dr. Pius Augustine, SH College, Kochi

15. Ampere’s swimming rule
Dr. Pius Augustine, SH College, Kochi

16. Imagine a swimmer, swimming in the
direction of current and always looking
towards the magnetic needle, such that
current enters from his head and leaves
from his head. The direction in which the left
hand of the swimmer points , gives the
direction of motion of north pole of the
magnetic needle.
Dr. Pius Augustine, SH College, Kochi

17. What will happen to a compass
needle when a compass is
placed below a wire and a
current is made to flow through
the wire? Give reason to justify
your answer.
Dr. Pius Augustine, SH College, Kochi

18. Describe a set up for
plotting the magnetic field
lines in a straight
conductor carrying
current Dr. Pius Augustine, SH College, Kochi

19. Describe an experiment to
demonstrate that there is a
magnetic field around a
current carrying conductor.
Dr. Pius Augustine, SH College, Kochi

20. Expt : B due to a straight conductor carrying current
X
Y
Dr. Pius Augustine, SH College, Kochi

21. How is magnetic field due to
straight current carrying wire
is affected if current in wire is
a) decreased b) reversed.
Dr. Pius Augustine, SH College, Kochi

22. Circular magnetic field around current
carrying conductor
Dr. Pius Augustine, SH College, Kochi

23. Draw diagram showing
the magnetic field lines
due to a straight wire
carrying current.Dr. Pius Augustine, SH College, Kochi

24. Dr. Pius Augustine, SH College, Kochi

25. Properties magnetic field lines due to a
straight conductor
1. Concentric circles with
common centre on the
conductor.
2. Far away – slightly elliptical
due to earth fieldDr. Pius Augustine, SH College, Kochi

26. 3. Direction of field reversed on
reversal of current direction.
4. Plane of field – perpendicular
to conductor.
Properties magnetic field lines due to a
straight conductor
Dr. Pius Augustine, SH College, Kochi

27. 5. Flux density -
strength of B.
6. Conductor is within
cylindrical shell of B
Properties magnetic field lines due to a
straight conductor
Dr. Pius Augustine, SH College, Kochi

28. Magnetic field of earth
Dr. Pius Augustine, SH College, Kochi

29. How can we find the direction of
magnetic field due to a straight
current carrying conductor ?
right hand thumb rule
Dr. Pius Augustine, SH College, Kochi

30. State a law, which
determines the direction
of magnetic field around a
current carrying wire?
Dr. Pius Augustine, SH College, Kochi

31. State right hand thumb rule
Dr. Pius Augustine, SH College, Kochi

32. Imagine a current carrying conductor
held in your right hand such that the
thumb points in the direction of
current, then the curl of your fingers
encircling the conductor will give the
direction of magnetic field lines
around the conductor.
Dr. Pius Augustine, SH College, Kochi

33. Maxwell’s cork (RH)
screw rule
Imagine a right handed screw to be
rotated in the direction of current, then
the direction of rotation gives the
direction of magnetic field lines.
Dr. Pius Augustine, SH College, Kochi

34. Dr. Pius Augustine, SH College, Kochi

35. Expt: B due to a circular current carrying loop
Dr. Pius Augustine, SH College, Kochi

36. Two parallell conductors
carrying equal currents in
the same direction
Plot lines of forces around
them?
Dr. Pius Augustine, SH College, Kochi

38. Dr. Pius Augustine, SH College, Kochi

40. Two parallel conductors
carrying equal currents in
the opposite direction
Plot lines of forces around
them? Dr. Pius Augustine, SH College, Kochi

41. Dr. Pius Augustine, SH College, Kochi

42. Dr. Pius Augustine, SH College, Kochi

43. Magnetic field due to current loop
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44. Draw a labeled diagram
showing the three magnetic
lines of a loop carrying current.
Mark the direction of current
and direction of magnetic field
by arrows in your diagram
Dr. Pius Augustine, SH College, Kochi

45. 1. Uniform near the centre of the
coil.
2. Lines of force near the centre
appear to be entering through one
face of the coil and leaving through
the other face.
Field due to current loop :
Dr. Pius Augustine, SH College, Kochi

46. 3. Face – lines flow in – current
is clockwise – south polarity S
4. Face – lines flow out – current
is anticlockwise – north polarity
N
Dr. Pius Augustine, SH College, Kochi

47. Solenoid
Conducting wire wound in
the form of a cylindrical coil
whose diameter is less in
comparison to length, is
called a solenoid.Dr. Pius Augustine, SH College, Kochi

48. Solenoid field – expt.
Dr. Pius Augustine, SH College, Kochi

49. Dr. Pius Augustine, SH College, Kochi

50. Dr. Pius Augustine, SH College, Kochi

51. Draw a diagram to
represent the magnetic
field lines along the axis
of a current carrying
solenoid. Dr. Pius Augustine, SH College, Kochi

52. Solenoid – explanation
1. Behaves like a magnet,
whose strength depends on
current through it.
2. South pole – end where
current appears clockwise.Dr. Pius Augustine, SH College, Kochi

53. 3. North pole – end where current
appears anticlockwise.
4. Field direction – N to S outside,
S to N inside.
Solenoid – explanation
Dr. Pius Augustine, SH College, Kochi

54. 5. Field – uniform inside, nonuniform
outside.
6. Field inside B = μ0μrnI
μ0 - Absolute permeability
μ r - Relative permeability
n - no. of turns/unit length
I - current flowing through the coil
Solenoid – explanation
Dr. Pius Augustine, SH College, Kochi

55. Name and state the rule
by which the direction of
magnetic field in a
current carrying solenoid
is determined.Dr. Pius Augustine, SH College, Kochi

56. What effect will there be on a
magnetic compass when it is
brought near a current carrying
solenoid?
Needle takes the direction of
magnetic field of solenoid.Dr. Pius Augustine, SH College, Kochi

57. State two ways by
which magnetic field
due to a solenoid can
be made stronger.
Dr. Pius Augustine, SH College, Kochi

58. Why does a current
carrying freely
suspended solenoid
rests along a particular
direction ? Dr. Pius Augustine, SH College, Kochi

59. A soft iron is introduced inside a
current carrying solenoid. The
magnetic field inside the
solenoid is …………………..
Will increase
Dr. Pius Augustine, SH College, Kochi

60. The magnetic field lines
inside a current carrying
solenoid are …………
Along the axis and parallel
to each other.
Dr. Pius Augustine, SH College, Kochi

61. What is a solenoid ?
A cylindrical coil of many tightly
wound turns of insulated wires
with generally diameter of the
coil smaller than its length is
called a solenoid.
Dr. Pius Augustine, SH College, Kochi

62. Dr. Pius Augustine, SH College, Kochi

63. Dr. Pius Augustine, SH College, Kochi

64. You are required to make an electromagnet
from a soft iron bar. Draw a circuit
diagram to represent the process. In your
diagram you are required to show a cell,
an insulated copper coil, the soft iron bar
and a switch. Label the poles of the
electromagnet.
Dr. Pius Augustine, SH College, Kochi

65. Dr. Pius Augustine, SH College, Kochi

66. Electromagnet
Artificial magnet
Made from a piece of soft iron,
by passing electric current in a
coil wound around it .
Two types
1.I shaped (bar magnet )
2.U shaped (horse shoe magnet)
Dr. Pius Augustine, SH College, Kochi

67. Construction of I – shaped electromagnet.
Wind thin insulated copper wire in the form
of a solenoid around a soft iron bar PQ
The ends of the wire are connected to a
battery, through a key.
Press key.
Used in relays (switching device)
Dr. Pius Augustine, SH College, Kochi

68. Dr. Pius Augustine, SH College, Kochi

69. Construction of horse shoe
electromagnet.
Wound thin insulated copper
wire on the arms of U shaped
soft iron core.
Windings in the two arms should
be in opposite sense .
Clockwise – S pole
Anticlockwise - N pole.
Dr. Pius Augustine, SH College, Kochi

70. Factors affecting strength
of electromagnet.
i. Increasing no. of turns
ii.Increasing current through
the coil.
Dr. Pius Augustine, SH College, Kochi

71. What is an
electromagnet? State
two factors on which
the strength of magnetic
field of electromagnet
depends.
Dr. Pius Augustine, SH College, Kochi

73. Lifting electromagnet
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83. Magno-Voltron: NASA's New Electromagnetic Spacecraft
Dr. Pius Augustine, SH College, Kochi

84. Uses of electromagnet
i. To lift big iron pieces (20,000 kg)
ii. Loading furnace with iron
iii.Removing iron from wounds
iv.Electric bell, fan, generator,
microphone, loud speaker etc
v. Magnetic separation
vi.Magnetic levitation
Dr. Pius Augustine, SH College, Kochi

85. State two ways through which the
strength of an electromagnet can be
increased.
i. Increasing no. of turns of coil
ii. Increasing current through coil
iii. Core of higher mangetic
permeability
iv. Increase diameter of coil (area of
cross section) Dr. Pius Augustine, SH College, Kochi

86. Dr. Pius Augustine, SH College, Kochi

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90. Dr. Pius Augustine, SH College, Kochi

91. Permanent magnet
Made from steel.
Once magnetised doesnot loose
magnetism easily (has more
retentivity than iron)
Used in galvanometers, ammeters
voltmeters, magnetic compass, bar
magnet used in labs etc.

92. Dr. Pius Augustine, SH College, Kochi

93. State two advantages of
electromagnet over
permanent magnet.
Dr. Pius Augustine, SH College, Kochi

94. State two difference
between permanent
magnet and
electromagnet.
Dr. Pius Augustine, SH College, Kochi

95. Dr. Pius Augustine, SH College, Kochi

96. Electric bell
Dr. Pius Augustine, SH College, Kochi

97. Electric bell
1.Horse shoe electromagnet :
large no. of turns of copper
wire wound over U- shaped
soft iron bar. When current is
passing it acts as horse shoe
magnet. Dr. Pius Augustine, SH College, Kochi

98. Electric bell
2. Armature : soft iron bar
suspended from a stud ‘s’ with
the help of a flat steel spring
such that armature faces the
poles of electromagnet
Dr. Pius Augustine, SH College, Kochi

99. Electric bell
3. Metallic spring strip : Flat
steel spring ,slightly bent
and fixed to the armature
using screws.
Dr. Pius Augustine, SH College, Kochi

100. 4. Make and break arrangement (contact
adjustment screw) :
Two sharp pointed tips of silver
cadmium alloy – one attached to
spring strip and other in a conducting
pillar of brass.
Tip on brass pillar can be moved
forward or backward for getting
Dr. Pius Augustine, SH College, Kochi

101. 5. Hammer and gong:
Hammer is made of steel and is
attached to armature. Gong is
made of brass.
Dr. Pius Augustine, SH College, Kochi

102. Working: On pressing bell push,
i.Electromagnet gets activated and
pulls the soft iron armature.
ii.Flat spring b/w stud and armature
is under tension .
iii.Hammer strikes gong and makes
sound. Dr. Pius Augustine, SH College, Kochi

103. Working: On pressing bell push,
4. Ag-Cd tips are detached, circuit – off,
demagnetised, hammer continued
due to inertia and hits gong.
5. Flat spring brings armature back and
circuit is on again and process is
repeated.
Dr. Pius Augustine, SH College, Kochi

104. Show with the aid of a diagram how
a wire is wound on a U- shaped
piece of soft iron in order to make
it an electromagnet. Complete the
circuit diagram and label the poles
of the electromagnet.
Dr. Pius Augustine, SH College, Kochi

105. Why is soft iron used as the core of
the electromagnet in electric bell ?
Soft iron has high magnetic permeability.
Hence it can be magnetised strongly
and demagnetised easily.
It intensifies the magnetic field of
solenoid helps in making a strong
magnet. Dr. Pius Augustine, SH College, Kochi

106. How is the working of
electric bell affected, if
alternating current be
used instead of direct
current ? Dr. Pius Augustine, SH College, Kochi

107. For my youtube videos: please visit -
SH vision youtube channel
or
xray diffraction series
SH Vision
Dr. Pius Augustine, S H College, Kochi

108. 108
Appeal: Please Contribute to Prime Minister’s or Chief
Minister’s fund in the fight against COVID-19
Dr. Pius Augustine, Dept of Physics, Sacred Heart College, Thevara
we will
overcome
Thank You
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Dr. Pius Augustine, Asst. Professor, Sacred Heart College, Thevara, Kochi.