cbse 12th physics investigatory project with observations
Aim: To trace the magnetic lines of force of a bar magnet.
Apparatus: 2 Bar magnets, thick paper, iron filings etc.
Theory: Many similarities exist between electric and magnetic phenomena. A magnet has two opposite poles,
referred to as north and south. Opposite magnetic poles attract each other, and similar magnetic poles repel
each other, exactly as happens with electric charges. When a magnet is kept at a place, it influences the space
surrounding itself. The effect a magnet has around its surrounding is called the magnetic field of the magnet.
Magnets are surrounded by magnetic fields. A magnetic field can be thought of as consisting of lines of force.
The forces of magnetic attraction and repulsion move along the lines of force. A magnet has two opposite
poles, referred to as north and south. Opposite magnetic poles attract each other, and similar magnetic poles repel
each other, exactly as happens with electric charges.
Figure 1 Figure 2
Figure 3 Figure 4
The force with which magnetic poles attract or repel each other depends on the strength of the poles and the distance
between them. The properties of lines of force can be enumerated as:
1. They are said to originate from the north pole and end at the south pole. This is only a convention.
2. The lines of forces of a particular magnet do not intersect with each other.
3. Tangent to the line of force gives the direction of the magnetic field acting at that point.
4. A line of force is continuous: starts from the North Pole and ends at the South Pole.
5. There is no line of force within the magnet.
Procedure : In the following experiment you will trace the magnetic lines of force of a bar magnet .The bar magnet is
a surface containing iron filings.
1. Place a plain, thick paper on a table and support it such that it remains flat.
2. Spread fine iron filings on the paper & Place a bar magnet on the paper
4. Tap the paper gently. Write detailed observation regarding the arrangement of iron filings around the magnet
5. Now take 2 bar magnets and place them as show in figure 1, 2 and 3 respectively.
6. Write detailed observation regarding the arrangement of iron filings around the magnets The iron filings line up
along the magnetic field lines of the magnet. Note the circular pattern of the field lines.
By convention, we say that the field lines emanate from the north pole of the magnet and re-enter the magnet
through the South Pole. Note also that the field lines are closer together at the poles than at the center of the
magnet. More iron filings are attracted to the poles because the strength of the magnetic field is greater at the poles.