The number or coefficient expressing the relative dielectric capacity of a medium or substance.

A non-conductor; a substance, the different parts of which may, after an electric disturbance, remain, without any process of readjustment, and for an indefinite period of time, at potentials differing to any extent (Daniell). There is no perfect dielectric. The term dielectric is generally only used when an insulator acts to permit induction to take [...]

(a) In telephones and microphones a disc of iron thrown into motion by sound waves or by electric impulses, according to whether it acts as the diaphragm of a transmitter or receiver. It is generally a plate of japanned iron such as used in making ferrotype photographs. (b) A porous diaphragm is often used in [...]

A tuning-fork or diapason kept in vibration by electricity. In general principle the ends of the fork act as armatures for an electro-magnet, and in their motion by a mercury cup or other form of contact they make and break the circuit as they vibrate. Thus the magnet alternately attracts and releases the leg, in [...]

The points on the commutator of a closed circuit ring–or drum–armature, which the brushes touch, and whence they take the current, mark the extremities of the diameter of commutation. Were it not for the lag this would be the diameter at right angles to the line connecting the centers of the opposite faces of the [...]

(a) The science or study of diamagnetic substances and phenomena. (b) The magnetic property of a diamagnetic substance.

Treating diamagnetism as due to a polar force, the polarity of a diamagnetic body is the reverse of the polarity of iron or other paramagnetic bodies. A bar-shaped diamagnetic body in a field of force tends to place itself at right angles to the lines of force.

An apparatus for use in chemical analysis for testing the purity of substances by the time required for a charged surface to be discharged through them to earth. It is the invention of Rousseau. An electrometer is charged with a dry pile. One of its terminals is connected with one surface of the solution or [...]

Possessing a negative coefficient of magnetic susceptibility; having permeability inferior to that of air. Such substances placed between the poles of a magnet are repelled; if in the form of bars, they tend to turn so as to have their long axis at right angles to the line joining the poles. The reason is that [...]

A medical diagnosis of a patient’s condition based on the action of different parts of the body under electric excitement.