Question

What is the sure test of magnetism?

Answer 1

Hint: We will determine what the main properties of a magnet are. Then we will think about which properties are also found in other objects that are non-magnets. Finally, we can figure out how to distinguish a magnet from any other similar objects.

Complete solution:
The main three properties that a magnet show are the following-
Attraction, induction, and repulsion
Attraction is the most common property one can think about considering a magnet. Attraction takes place between two unlike poles of magnets. However, if we think broadly, a magnet can also attract metals like iron, nickel, and cobalt. Therefore, attraction is not a sure test of magnetism.
Magnetism can be induced in metals such as iron, nickel, and cobalt. We make artificial magnets for industrial purposes by inducing magnetism to those metals. This implies that also, Induction is not a sure test of magnetism.
Now continue with the last property, i.e., repulsion. Repulsion can only take place between two like poles of a magnet.
By attraction, one can not say if a substance is magnetic or not, but if two objects repel each other, one can be sure that those two objects are magnets. Hence, Repulsion is the sure test for magnetism.

Note: In our daily life, we can observe attraction in many other cases, such as attraction by static charges and attraction of two unlikely charged objects. In both cases, the electric force is behind this attraction. The electric force also has the same nature as the magnetic force has- like charge repels each other and unlike charge attracts each other.