Magnetic lines of force Practical for standard 8 to 12

 Experiment 1:   
Magnetic lines of  force around a bar magnet. 

Aim :- 
To draw the magnetic lines of force around a bar magnet.

Materials required :- 
Drawing board, brass pins, a sheet of paper, a bar magnet, a magnetic compass, a pencil and a scale. 

Procedure :-  Fix the paper on the drawing board using brass pins so that there are no wrinkles. Place the compass in the middle of the sheet and mark the North-South direction by putting dots against the poles. Remove the compass and draw a straight line through these dots.

Note :- 
Do not disturb the drawing board till the experiment is complete. 

 

Northe South direction

Magnetic lines of force around magnet

Special instruction

The compass may not show any  specific direction at certain places around the magnet and may behave indifferently. Locate such points. (neutral points).

On the basis of your observations in the above experiment state whether the following  statements are
true or false. Correct if necessary.

1.The magnetic lines of force start at one pole and end at the other.

2.The magnetic lines of force do not intersect each other.

3.The pattern of the magnetic lines of force depends on the position of the magnet with respect to the geographical poles of the earth.

Remember

 The magnetic lines of force start at one pole and end in the   other. But conventionally the lines of force are considered   to start at the north pole and end in the south pole.

 The magnetic lines of force do not intersect each other.

Magnetic field : 

Experiments have shownthat a magnet or a current carrying conductor can exert force on the nearby magnetic substances even when they are not in touch with each other. It implies that there is a magnetic force around a magnet or a current carrying conductor. The area in which magnetic force is present and magnetic effect is felt is called magnetic field. 

Detection of the presence of a magnetic field.
Keep a magnetic needle in the area to be tested. If the magnetic needle deflects, then it means that there is a magnetic field. Usually magnetic field is represented by a set of lines. These lines are called magnetic lines of force. Why is magnetic field represented by a set of lines ? Magnetic field or magnetic lines of force are invisible. The fact that the iron filings arrange themselves along a few curved lines (fig 1.12(b)) in a magnetic field might have resulted in the concept of lines of force. The magnetic lines of force can also be traced by a magnetic needle. The pattern of magnetic lines of force depends on the shape of the magnet and its strength. Therefore the pattern of magnetic lines will be different for different magnets. The study of magnetic lines of force around a powerful bar magnet reveals the following properties.