http://www.ck12.org Chapter 20. Magnetic Fields
Review
Questions
- Magnetism is always present when electric charges ___.
- What happens to the strength of an electromagnet if the number of loops of wire is increased?
- What happens to the strength of an electromagnet if the current in the wire is increased?
- Which direction does the magnetic field point in the solenoid sketched here?
- solenoid:A current-carrying coil of wire that acts like a magnet when a current passes through it.
- electromagnet:A temporary magnet consisting of an iron or steel core wound with a coil of wire, through
which a current is passed. - magnetic levitation:The suspension of an object above a second object by means of magnetic repulsion.
Magnets can be temporary or permanent, depending on their ability to retain charge when not in contact with another
magnet. Ferromagnetic materials are substances that can be made into magnets. A ferromagnetic core wrapped with
a current-carrying wire forms an electromagnet that may be many times stronger than the magnet alone. Magnets
emit magnetic fields, and passing a wire connected to a complete circuit through such fields induces current through
the circuit. This is the basic premise behind electrical generators, effectively converting the mechanical energy of
the motion of the wire into electrical energy.