Fig. 5.—The Lifting Power of a Bar Magnet. It must be brought closer to the nails than the tacks because they are heavier.
Place some small carpet-tacks on a piece of paper and hold a magnet above them. Gradually lower the magnet until the tacks jump up to meet it.
Then try some nails in place of the tacks. The nails are heavier than the tacks, and it will require a greater force to lift them. The magnet will have to be brought much closer to the nails than to the tacks before they are lifted, showing that the force exerted by the magnet is strongest nearest to it.
Magnetize a needle and lay it on a piece of cork floating in a glass vessel of water. It will then be seen that the needle always comes to rest lying nearly in a north and south line, with the same end always toward the north.
Fig. 6.—A Simple Compass.
The pole of the magnet which tends to turn towards the north is called the north-seeking pole and the opposite one is called the south-seeking pole.
The name is usually abbreviated to simply the north and south poles. The north pole of a magnet is often indicated by a straight line or a letter N stamped into the metal.
A magnetized needle floating on a cork in a basin of water is a simple form of