Title of Experiment:
Course:
Name(s):
Instructor:
Date:
Magnets in Action
Section:
Introduction and Objectives:
In this lab we will observe the geometry of magnetic field around a bar magnet and study its
properties.
Theory:
Just like electric field present around a charged particle, magnet also has magnetic field around
it. Each magnet has two poles, the north and the South Pole. Magnetic field emerges from the
North Pole and terminates on the South Pole.
Differences between magnetic fields and electric
fields:

Positive and negative charges can exist
separately. North and south poles always
come together. Single magnetic poles,
known as magnetic monopoles, have been
proposed theoretically, but a magnetic
monopole has never been observed.

Electric field lines have definite starting and
ending points. Magnetic field lines are
continuous loops. Outside a magnet the field
is directed from the North Pole to the South
Pole. Inside a magnet the field runs from
south to north.
Figure 1: Magnetic field line in a bar magnet
We will also be using a magnetic compass to help
determine the geometry. A magnetic compass consists of a tiny magnet that would orient itself in
the direction of the magnetic field present at that point.
Equipment Required:
Magnets, iron filings, paper, cardboard, magnetic compass, gloves.
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Equipment Required
Paper and
cardboard
Magnets
Iron filings
Bowl to
collect iron
filings after
experiment
Magnetic
compass
Gloves (to
protect hands)
Lab Procedures:
Position the magnet(s) below the paper and cardboard in different arrangements as shown in
the figures below. Sprinkle small amounts of iron filings over the paper and tap it gently to make
the filings align with the field lines of the magnet(s). Sketch the patterns you see.
Example of pattern seen with a single bar magnet
Radiating
field lines
Concentration
at the poles
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i) Single bar magnet:
N
S
ii) Two bar magnets with opposite poles facing each other:
N
S
N
S
iii) Two bar magnets with their north poles facing each other:
S
N
N
3
S
iv) Predict these patterns:
a)
S
N
N
S
S
N
N
b)
S
N
S
N
N
S
S
N
c)
v)
a) Is it possible to arrange 3 bar magnets to produce the pattern shown below?
b) Does the above pattern represent attraction or repulsion?
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S
vi)
a) Is it possible to arrange 3 bar magnets to produce the pattern shown below?
b) Does the above pattern represent attraction or repulsion?
vii) If you see the magnetic field pattern in the figure below, can you be certain which is the
north pole? Why?
viii) If you see the magnetic field pattern in the figure below, can you be certain which are the
north and south poles of the magnets? Explain.
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ix) Label the remaining poles in the figure:
N
x) Label the remaining poles in the figure:
N
xi) Label the remaining poles in the figure:
N
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xii) Indicate if the following patterns are possible or not. Explain your reasoning.
Possible: Yes or No?
Possible: Yes or No?
Based on above observations, is it necessary that a magnetic field start at north pole and end at
the south pole of the same magnet?
Conclusions:
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