Câu hỏi:

Magnets

A solid object that has the power to attract iron and some metals is called a magnet. It does this through its magnetic field, a region of force surrounding it. The (1) _______ the magnet, the more intense is the field.

Objects that are attracted to the magnet feel a force (2) _______ as magnetism when they are inside the magnetic field. This magnetic force can pass through some materials. Even a weak magnet will attract a pin to the other side of a sheet of paper, for example.

Magnets come in (3) _______ shapes. A familiar one is the curved horseshoes magnet. There are also bar magnets in the form of disc or a stubby cylinder. Every magnet has (4) _______ poles, called north and south, at opposite ends of it: at the two ends of a horseshoes magnet, for example, or on the two sides of a disc.

Powerful magnets can be made by passing an electric current through wire coiled around a piece of iron. The (5) _______ is called and electromagnet. Magnets are used in many household and everyday devices. They are also commonly used in industrial machinery, usually in the form of electromagnets.

The (1) _______ the magnet, the more intense is the field.