A law of thermo-electricity. In a homogeneous circuit, however, the temperature varies from point to point; there is no current. Whatever potential differences may be established by the variations in temperature it is evident that they must counteract each other and reduce to zero.

An apparatus for producing a loud sound, involving the principles of the telephone. A rapidly alternating or make and break current being produced by any means and being transmitted through the telephone gives a loud note of pitch dependent on the current producing it. Sometimes a perforated metallic disc is rotated in a magnetic field, [...]

No such thing as a unipolar magnet is possible. The name is given to poised or suspended magnets, one of whose poles lies in the axis of suspension. It is obvious that such a magnet will act, as far as its directive tendency and rotatory movements are concerned, as if it had only one pole. [...]

A magnet coil with movable or loose axial bar of soft iron. The whole is usually mounted vertically. When a strong enough current is passed the bar is drawn up into the coil as if by suction, whence the name.

A magnet which is so uniformly magnetized and is so long in proportion to its other dimensions that it virtually establishes two magnetic poles, one at either end. It is a long thin bar so magnetized that all its molecules would, considered as magnets, be absolutely equal. (Daniell.) It acts like a solenoid, except that [...]

A magnet made of one piece of metal, or at least magnetized as such; the reverse of a compound magnet, which is magnetized piece by piece and then fastened together.

The power of sustaining a weight by attraction of its armature possessed by a magnet. In general terms the adherence of the armature of a magnet to the pole varies with the square of the number of lines of force which pass through the point of contact. Hence an increased adherence of the armature to [...]

A unit magnet pole is one which exerts unit force on another unit pole placed at unit distance from it. Unit force is the dyne; unit distance is one centimeter.

Magnet poles are often not situated at the ends. Owing to inequality of the material or other causes they may occupy intermediate positions on the magnet. Such poles are called secondary poles.

The part of a magnet showing strongest polarity; the part which attracts iron the most powerfully, and acts as the starting point for lines of force.