A rod is charged by rubbing it on a cloth. When the rod touches the metal sphere, some electric charge is transferred down the strings to the two small white balls. They therefore both have charge of the same sign as that on the rod. They immediately separate a little from each other. They no longer hang vertically downwards, because of the extra electric force acting between them.

This shows that, in electricity, charges of the same type repel each other. Positive repels positive and negative repels negative. It is also true that positive attracts negative, and vice versa, but we don't show that here (if it's a dry day, try an experiment yourself). In electricity, like charges repel and opposites attract.

Here, the magnetic forces that the wires exert on each other push the wires together. Two electric currents travelling in the same direction experience an attractive force. Electric currents are carried by moving electric charge (electrons in the case of metal wire), so if electric charges of the same sort travel in the same direction parallel to each other, the magnetic force is attractive. In magnetism, like currents attract and opposite currents repel.

Safety warning. The currents involved in the second demonstration are quite large (they are produced by short circuiting a 12 volt car battery and probably exceed 100 Amperes). This demonstration is a bit dangerous: it produces sparks and, if the current flows for more than a few seconds, the wires and contacts become very hot. The battery could also get hot. Do not do it unless you know what you're doing.