Electricity for Boys Part 18

2. The electro-motive force is equal to the current strength multiplied by the resistance.

3. The resistance is equal to the electro-motive force divided by the current strength.

Overload. In a motor an excess of mechanical work which causes the armature to turn too slowly and produces heat.

Phase. One complete oscillation. The special form of a wave at any instant, or at any interval of time.

Plate, Condenser. In a static machine it is usually a plate of gla.s.s and revoluble.

Plate, Negative. The plate in a battery, such as carbon, copper or platinum, which is not attacked by the solution.

Plating, Electro-. The method of coating one metal with another by electrolysis.

Polarity. The peculiarity, in a body, of arranging itself with reference to magnetic influence.

Parallel. When a number of cells are coupled so that their similar poles are grouped together. That is to say, as the carbon plates, for instance, are connected with one terminal, and all the zinc plates with the other terminal.

Polarization. When the cell is deprived of its electro-motive force, or any part of it, polarization is the result.

It is usually caused by coating of the plates.

Porosity. Having small interstices or holes.

Positive Current. One which deflects a needle to the left.

Positive Any current flowing from the active element, Electricity. such as zinc, in a battery. The negative electricity flows from the carbon to the zinc.

Potential, Electric. The power which performs work in a circuit.

Potential Energy. That form of force, which, when liberated, does or performs work.

Power Unit. The volt-amperes or watt.

Primary. The induction coil in induction machines, or in a transformer.

Push b.u.t.ton. A thumb piece which serves as a switch to close a circuit while being pressed inwardly.

Quant.i.ty. Such arrangement of electrical connections which give off the largest amount of current.

Receiver. An instrument in telephony and telegraphy which receives or takes in the sound or impulses.

Relay. The device which opens or closes a circuit so as to admit a new current which is sent to a more distant point.

Repulsion, That tendency in bodies to repel each other when Electric. similarly charged.

Resilience. The springing back to its former condition or position. Electricity has resilience.

Resistance. The quality in all conductors to oppose the pa.s.sage of a current.

Resistance Coil. A coil made up of wire which prevents the pa.s.sage of a current to a greater or less degree.

Resistance, The counter force in an electrolyte which seeks Electrolytic. to prevent a decomposing current to pa.s.s through it.

Resistance: Internal, The opposing force to the movement of a current External. which is in the cell or generator. This is called the _internal_. That opposite action outside of the cell or generator is the _external_.

Resonator, An open-circuited conductor for electrically Electric. resounding or giving back a vibration, usually exhibited by means of a spark.

Rheostat. A device which has an adjustable resistance, so arranged that while adjusting the same the circuit will not be open.

Safety Fuse. A piece of fusible metal of such resistance that it breaks down at a certain current strength.

Saturated. When a liquid has taken up a soluble material to the fullest extent it is then completely saturated.

Secondary. One of the two coils in a transformer, or induction coil.

Secondary Plates. The brown or deep red plates in a storage battery when charged.

Self-excited. Producing electricity by its own current.

Series. Arranged in regular order. From one to the other directly. If lamps, for instance, should be arranged in circuit on a single wire, they would be in series.

Series, Multiple. When lamps are grouped in sets in parallel, and these sets are then connected up in series.

Series Windings. A generator or motor wound in such a manner that one of the commutator brush connections is joined to the field magnet winding, and the other end of the magnet winding joined to the outer circuit.

Shunt. Going around.

Shunt Winding. A dynamo in which the field winding is parallel with the winding of the armature.

Snap Switch. A switch so arranged that it will quickly make a break.

Sounder. The apparatus at one end of a line actuated by a key at the other end of the line.

Spark Coil. A coil, to make a spark from a low electro-motive force.

Spark, Electric. The flash caused by drawing apart the ends of a conductor.

Specific Gravity. The weight or density of a body.

Static Electricity. Generated by friction. Also lightning.

Any current generated by a high electro-motive force.

Strength of Current. The quant.i.ty of electricity in a circuit.

Synchronize. Operating together; acting in unison.

Terminal. The end of any electric circuit or of a body or machine which has a current pa.s.sing through it.

Thermostat, Electric. An electric thermometer. Usually made with a metal coil which expands through the action of the electricity pa.s.sing through it, and, in expanding, it makes a contact and closes a circuit.

Transformer. The induction coil with a high initial E. M. F.