Hobbies And Interests
Prolonged Contact With a Magnet
The fastest way to magnetize a nail involves creating prolonged contact with a permanent magnet of sufficient strength. You can purchase permanent magnets in hardware and hobby supply stores and even in junkyards. Often made of hard steel, permanent magnets retain most of their magnetism once they've been magnetized. If held in contact with one end of a nail for some time, the nail will begin to exhibit magnetism and will be able to pick up small iron objects such as paper clips and iron filings with the opposite end. It will, however, go back to normal once it breaks contact with the permanent magnet.
Rubbing With a Magnet
Rubbing the nail with the permanent magnet causes a stronger, more lasting magnetism in the nail. For this to work, only one pole of the magnet must stroke the nail from one end to the other in a single direction. The magnet must be lifted completely off the nail after each stroke before beginning the next one. The nail's magnetism increases with each stroke. It usually takes around 20 to 30 strokes before the nail becomes sufficiently magnetized. Stroking with one pole of a permanent magnet works because it aligns the molecules in the nail in the same polar direction, giving the nail a positive and a negative end.
Using Batteries
The third method of magnetizing a nail uses electromagnetism and requires the use of a length of insulated copper wire, some pliers and a battery or series of batteries taped together. About an inch of copper wire needs to be exposed from either end, while the middle portion of the wire wraps tightly about the nail. Attaching each exposed end of the copper wire to opposite battery terminals completes the electromagnet. Current flowing through the wire in a loop around the nail creates a magnetic field. The electromagnet becomes stronger with each additional coil twisting around the nail. Increasing the battery voltage has the same effect.
Demagnetizing
To make the class understand that the magnetism created was only temporary, the teacher can then demonstrate ways of demagnetizing the nail. To demagnetize a nail magnetized by prolonged contact or rubbing, banging the nail on a hard surface or dropping it to the floor works instantly by shaking up the aligned molecules with sharp impact. For the electromagnet, simply detaching one end of the copper wire from its terminal kills the magnetic field.