Simple Motor

Aim:

To make a simple home-made motor.

Materials required:

• A thick walled paper or plastic cup.
• Two large metal paper clips.
• Five small circular or bar magnets.
• 60 cm of insulated 20 gauge copper wire.
• Insulation tape.
• Two code wires- insulated wires with alligator clips on the ends.
• A 1.5 volt battery or two for better results.
• Battery holder.
• Wire stripper.
• Black waterproof marking pen.
• Two thick straws.

Procedure:

• Wind the insulated copper wire into a coil with about four or five loops with around 2.5 cm diameter. Leave some length at both ends free.
• Warp the uncoiled ends around the coil in opposite direction to the loops to keep the coil firmly in place as a coil. Leave 5 cm protruding at both ends after doing this.
• Use the wire stripper to strip off the insulation at both protruding ends of the coil.
• Use the black marker to colour one side of one protruding end of the coil. That is, if you turn the wire around you should be able to see the black colour only on one side.
• Keep the cup upside down on a desk and place two magnets on top of it and three magnets on the other side so that the magnets remain attached to each other, even through the closed end of the cup.
• Tape thick straws to both sides of the cup. Cut the straws down to size as required later.
• Use the protruding end of the paper clips to clip it onto the straws.
• Connect the winded copper wire coil to the paper clips in such a way that only one side of the wire is touching any part of the metal clip at one time. That is, either the black coloured end alone should be in contact with the paper clip or the other side. You can use the insulated part of the copper wire to ensure that the other side does not come into electrical contact with the metal paper clip.
• Cut the straw down to size in such a way that the coil is suspended from the paper clips above the magnets without touching them, but still very close. The coil should be able to spin freely.
• Now use the alligator clips on the code wires to connect them to each paper clip.
• Connect the other ends of the code wires to the terminals of the batteries through the battery holder.
• Give the coil a slight push on one side of the diameter to make it start spinning. You will see that it continues to spin on its own. If it does not, make sure that assembly is balanced properly and that the coil is not too far away from the magnets. Also check if the electrical contact is proper with the paper clips.
• Keep adjusting the assembly till the coil starts spinning continuously after being started off.

Scientific explanation:

The permanent magnets kept on the cup have a magnetic field. When current flows through the copper wire coil, it also acts as an electromagnet with north and south poles. These poles will attract the unlike pole of the permanent magnet and repel the like pole. This will make the coil spin.

However if we had not used black colour on one side of the copper wire contact, as soon as the coil spins to a position where unlike poles of the electromagnet and permanent magnet  are close to each other, it would stop spinning. However the black colour on the wire acts as an insulator which cuts off the current flow through the coil for half of each spin of the coil when that part comes in contact with the metal paper clip. At that time the electromagnet stops generating a magnetic field and hence the problem we mentioned does not happen. The momentum or inertia of the rotating coil will make it continue to spin a little more until again the non coloured part comes in contact with the clip and the rotating force starts working again. Thus the coil keeps rotating. This is how a simple motor works.