Activities:


Take a bar magnet and place a steel pin at some distance Nothing happens. Now bring a steel pin near the pole of the bar magnet. It will stick to the magnet.

Activities:


Take a drawing board and fix a smooth white sheet of paper on it with the drawing pins. Sprinkle fine powder of iron filing on it such that it is spread evenly on paper. Now place a bar magnet in the middle of the white sheet. Tap the drawing board gently. The iron fillings move and re-position them- selves in the form of curves. This activity shows that magnetic substances experience a force by a magnet.


· The space around the magnet where its influence can be detected is called magnetic field. Take a drawing board and fix a white sheet of paper on it place a magnet on white sheet and draw its boundary. Now place a small compass needle close to the north pole of the magnet and mark two pencil dots exactly at the end of the needle. Mark the points one and two. Now lift the compass and place it in such a way that one end of the compass points towards the point two. Now mark the new end as three. Repeat it till 7 numbers etc. Join the points to get a continuous curve. Thus one magnetic line force is traced. Repeat the process from the north pole of the magnet from a different point and trace another magnetic line of force.


· Each line is a closed continuous curve


· They originate at the North Pole and terminate at the south pole of a magnet.


· The lines are crowded near the poles where magnetic lines are strong.


They do not intersect each other. Any source of magnetism such as a magnet or an electromagnet, is surrounded by a magnetic field. That field can be detected by various devices, which can also give information about the direction of the field and even its strength.


A simple compass can detect a magnetic field and demonstrate its direction. Iron filings can be used to show the shape of a magnetic field. At the sophisticated level, a gaussmeter can detect a field and indicate its strength, as measured in gauss units.

Compass: A compass is simply a thin magnet or magnetized iron needle balanced on a pivot. It can be used to detect small magnetic fields. The needle will rotate to point toward the opposite pole of a magnet. It can be very sensitive to small magnetic fields.

Using a compass to show the magnetic field:


When you bring a compass near an item suspected of being magnetized or having a magnetic field, the compass will turn and point toward the appropriate pole of the object.


A famous experiment showed that a wire with DC electric current running through it created a magnetic field. When the electricity was turned on, a nearby compass moved to indicate a magnetic field was present.


By spreading fine iron filings or dust on a piece of paper laid on top of a magnet, you can see the outline of the magnetic lines of force or the magnetic field.
Iron filings and compasses show the shape and direction of the magnetic field


This experiment also shows that magnetism will act through many materials, such as paper. Would the experiment work if a sheet of iron were used to sprinkle the filings? What about aluminum foil?

Gaussmeters are used to measure the strength of a magnetic field. They use an electronic chip called a Hall effect device, which gives off a tiny electrical current when exposed to a magnetic field. The current is amplified with electronic circuitry and a meter shows the number of gauss (the units of magnetic field strength). These devices are used to detect and measure magnetic fields in scientific experiments, in industry and even in people's homes.