Do you know
 |
| compass |
Chinese were the first people to use the property of magnets to construct Mariner’s Compass.
Magnets are useful in many ways. As more and more uses of magnets came to be known, the need for powerful magnets of fixed shape became great. To fulfill this need, powerful magnets of required shapes are made. The powerful magnets of different shapes that are prepared are called artificial magnets. Artificial magnets have regular shapes and required magnetic strength. Artificial magnets are named on the basis of the artificial magnets with their names are shown below.
 |
| Bar magnet |
 |
| Magnetic Needle |
 |
| Horse Shoe Magnet |
Artificial magnets
Natural magnets occur in many areas of the world and have been used in China since at least 2,600 BC. These natural magnets are no longer used because it is easy to make artificial magnets. Electromagnets exist only as long as the electricity is on. Non-electric artificial magnets can be more permanent--depending on the material that is used to make them.
Create an artificial magnet by using electricity. When electricity flows through a wire--for example, when the wire is connected to a battery--a magnet field is generated around the wire. You can intensify this magnetic field by coiling the wire so that the overlapping magnet fields reinforce each other. The coil is an artificial magnet as long as the electricity is flowing.
Insert a metallic core into the coil of wire to concentrate the magnetic field. This system of power supply and coil of wire around a metallic core is known as an electromagnet. For most common metallic cores, most of the magnetism goes away when the electricity is turned off.
Construct an electromagnet by attaching both ends of a long wire to a battery and then coiling the center part of the wire around a large nail or a metallic bolt. When both ends of the wire are attached to the battery and electricity is flowing, the metallic core will act like a magnet--picking up small metallic objects. When the circuit is broken--by disconnecting a wire--the small objects will fall. The electromagnet is a magnet only as long as the electricity is flowing.
Make a more permanent artificial magnet by choosing a specially designed substance to make an electromagnet. Two of these substances are alnico and permalloy. If you make an electromagnet using one of these substances--and leave the electromagnet turned on for a while--the core remains magnetic after the electricity is turned off.
How to Make an Easy Electromagnet.
 |
| Dry Cell |
Dry Cell
An electromagnet produces a magnetic field through the addition of an electric current. The electricity will flow through a wire. To produce a strong magnetic field in one area, the wire of the electromagnet is coiled around a solid core. The more coils or thicker the wire, the stronger the magnetic field. Electromagnets are used in many devices, such as loudspeakers, generators, magnetic locks, mass spectrometers, relays and transformers. You can create a simple electromagnet with items found at home.
How to Make An Electromagnet.
 |
| Electromagnet |
Electromagnets are advantageous over permanent magnets in that they can be turned on and off at will. Electromagnets are relatively easy to build if you follow a few steps.
Take the circular piece of metal [magnet] and wind copper wire around it. The windings should be tight and close together
Connect one end of the covered copper wound wire to the output side of a switch.
Connect the negative(black) battery terminal to the negative input terminal on the switch.
Connect the positive battery terminal to the end of the wound wire on the magnet
Check that the circuit is complete, beginning at the negative terminal of the battery to the input side of the switch, then from the output side of the switch to the magnet windings, then back to the positive terminal of the battery.
Turn the switch to on and the magnet will work.
Apparatus: Circular piece of metal.
Covered copper wire.
Switch
Battery.
Battery.
