In electricity like charges repel, and in magnetism like poles repel. That means if you put the north pole of a magnet near the north pole of another magnet, they will push apart, just like when you put a negatively charge object next to one that also has a negative charge. Measuring strength It is not easy to measure the strength of a magnetic field, except perhaps to see how much force it takes to pull it from a piece of iron. A Gauss meter is used to measure a magnetic field. You don't see those meters too often, because their use is limited.
Every magnet has a north pole and a south pole.
A positive or negative electrical charge can stand alone, but a magnet always has a N and S pole. If you cut a magnet in half, each piece will still have a N and S pole. Detecting a magnetic field You have seen how magnets attract certain metals. That is one easy way to detect if an object is magnetic. There are some other ways to detect a magnetic field or its force.