What is a Magnetic Field?
Fields fill the space between matter and they determine how it is that bits of matter can exert forces on other bits of matter at a distance. There are several different fields in nature, and their reality is demonstrated by our observation of the forces with which they are associated. So, for example, gravitational fields determine how it is that objects with mass are attracted together by a gravitational force. Electric fields determine how it is that objects with electric charge are attracted together by an electric force, if they have opposite electric charge, or repelled from each other, if they have the same electric charge. Interestingly, unlike an electric field, a magnetic field only comes into play when electric charges are moving. Magnetic fields determine how it is that electric currents, composed of moving electric charges, exert forces on other electric currents. Consider, then, two parallel wires, each with an electric current flowing in the same direction. By virtue of
A magnet produces a vector field, the magnetic field, at all points in the space around it. It can be defined by measuring the force the field exerts on a moving charged particle, such as an electron. The force (F) is equal to the charge (q) times the speed of the particle times the magnitude of the field (B), or F = q*v x B, where the direction of F is at right angles to both v and B as a result of the cross product. This defines the magnetic field’s strength and direction at any point. What creates the magnetic field? A magnetic field can be created with moving charges, such as a current-carrying wire. A magnetic field can also be created by the spin magnetic dipole moment, and by the orbital magnetic dipole moment of an electron within an atom. What is the relationship between current flow and magnetic fields? This is the Right Hand Rule for magnetic field from flowing current, and for magnetic field in a coil. When current flows in a wire, a magnetic field is created around the wir
A magnetic field is an invisible field which exerts magnetic force on substances which are sensitive to magnetism. A classic example of a magnetic field is the field created by an iron magnet; to see how the energy in such a field works, you can place a small magnet under a piece of paper and sprinkle iron filings on it. As the filings respond to the magnetic field, they will slowly orient themselves along an axis. Larger examples of magnetic fields include the Earth’s magnetic field, and the magnetic fields which are created by other celestial bodies such as stars and planets. Many people think of magnetism as a property of metal, particularly iron, since common household magnets are made from iron. Electrical currents are actually the force behind magnetic fields, which form as electrical charges move around. On a large scale like an electromagnet, the magnetic field is created by passing current through wires. In the case of a household magnet, the field is created by the movements
Typically, most people have been exposed to the phenomena created when you lay a bar magnet on a table, place a piece of glass over it and sprinkle iron filings on the glass. What turns up is a pattern of lines formed by the iron filings going from one end of the magnet to the other. Although a magnetic field isn’t truly comprised of lines, the iron filings give a good visual representation of the bar magnet’s magnetic field. You may have also noticed that further away from the magnet there weren’t as many lines and close to the magnet they were quite concentrated. This is a good demonstration of one of the best magnetic shielding methods available. Move the source of the magnetic field away from the item to be shielded or move the item away from the field. Even if it isn’t practical to remove the item from the field any increased separation will lower the strength of the field to be shielded.
