Electricity for Boys Part 15

Capacity. The carrying power of a wire or circuit, without heating. When heated there is an overload, or the _capacity_ of the wire is overtaxed.

Capacity, Storage. The quant.i.ty of electricity in a secondary battery when fully charged, usually reckoned in ampere hours.

Carbon. A material, like c.o.ke, ground or crushed, and formed into sticks or plates by molding or compression. It requires a high heat to melt or burn, and is used as electrodes for arc lamps and for battery elements. It has poor conductivity, and for arc lamps is coated with copper to increase its conductivity.

Cell, Electrolytic. A vessel containing an electrolyte for electroplating purposes.

Charge. The quant.i.ty of electricity on the surface of a body or conductor.

Chemical Change. When a current pa.s.ses through electrodes in a solution, a change takes place which is chemical in its character. Adding sulphuric acid to water produces heat. If electrodes of opposite polarity are placed in such an acid solution, a chemical change is produced, which is transformed into electricity.

Choking Coil. An instrument in a circuit which by a form of resistance regulates the flow of the current, or returns part of it to the source of its generation.

Counter-electromotive Force. Cells which are inserted in opposition to a battery to reduce high voltage.

Circuit, Astatic. A circuit in an instrument so wound that the earth's magnetism will not affect it.

Circuit Breaker. Any instrument in a circuit which cuts out or interrupts the flow of a current.

Circuit, External. A current flows through a wire or conductor, and also along the air outside of the conductor, the latter being the _external circuit._

Circuit Indicator. An instrument, like a galvanometer, that shows the direction in which a current is flowing through a conductor.

Circuit, Return. Usually the ground return, or the negative wire from a battery.

Circuit, Short. Any connection between the mains or parallel lines of a circuit which does not go through the apparatus for which the circuit is intended.

Coherer. A tube, or other structure, containing normally high resistance particles which form a path or bridge between the opposite terminals of a circuit.

Coil. A wire, usually insulated, wound around a spool.

Coil, Induction. One of a pair of coils designed to change the voltage of a current of electricity, from a higher to a lower, or from a lower to a higher electro-motive force.

Coil, Resistance. A coil so wound that it will offer a resistance to a steady current, or reduce the flow of electricity.

Commutator. A cylinder on the end of the armature of a dynamo or motor and provided with a pair of contact plates for each particular coil in the armature, in order to change the direction of the current.

Compa.s.s. An apparatus which indicates the direction or flow of the earth's magnetism.

Condenser. A device for storing up electro-static charges.

Conductance. That quality of a conductor to carry a current of electricity, dependent on its shape for the best results.

Conduction. The transmission of a current through a rod, wire or conductor.

Conductivity. That quality which has reference to the capacity to conduct a current.

Conductor. Any body, such as a bar, rod, wire, or machine, which will carry a current.

Connector. A binding post, clamp, screw, or other means to hold the end of a wire, or electric conductor.

Contact. To unite any parts in an electric circuit.

Controller. The handle of a switchboard, or other contact making and breaking means in a circuit.

Converter. An induction coil in an alternating circuit for changing potential difference, such as high alternating voltage into low direct current voltage.

Convolution. To wind like a clock spring.

Core. The inner portion of an electro-magnet. The inside part of an armature wound with wire.

Core, Laminated. When the core is built up of a number of separate pieces of the same material, but not insulated from each other.

Coulomb. The unit of electrical quant.i.ty. It is the quant.i.ty pa.s.sed by a current of one ampere intensity in one second of time.

Couple, Electric. Two or more electrodes in a liquid to produce an electric force.

Current, Alternating. A natural current produced by the action of electro-magnets. It is a succession of short impulses in opposite directions.

Current, Constant. A current which is uniformly maintained in a steady stream.

Current, Induced. A current produced by electro-dynamic induction.

Current Meter. An apparatus for indicating the strength of a current.

An ammeter.

Current, Oscillating. A current which periodically alternates.

Current, Periodic. A periodically varying current strength.

Current, Undulating. A current which has a constant direction, but has a continuously varying strength.

Decomposition. The separation of a liquid, such as an electrolyte, into its prime elements, either electrically or otherwise.

Deflection. The change of movement of a magnetic needle out of its regular direction of movement.

Demagnetization. When a current pa.s.ses through a coil wound on an iron core, the core becomes magnetized. When the current ceases the core is no longer a magnet. It is then said to be _demagnetized_. It also has reference to the process for making a watch non-magnetic so that it will not be affected when in a magnetic field.

Density. The quant.i.ty of an electric charge in a conductor or substance.

Depolarization. The removal of magnetism from a permanent magnet, or a horse-shoe magnet, for instance. It is generally accomplished by applying heat.

Deposition, The act of carrying metal from one pole of a cell to Electrolysis. another pole, as in electroplating.

Detector. Mechanism for indicating the presence of a current in a circuit.

Diaphragm. A plate in a telephone, which, in the receiver, is in the magnetic field of a magnet, and in a transmitter carries the light contact points.

Dielectric. A non-conductor for an electric current, but through which electro-static induction will take place.