. The principles underlying radio communication . sually abbreviatedto emf. The larger the number of cells which are joined inthe circuit in such a way that their pressures will add, thegreater the electric pressure in the circuit and the larger the-current produced, just as the rapidity of flow of the water inthe pipe line may be increased by increasing the pump pressure. 24 RADIO COMMUNICATION. Resistance.—There is always some friction in pipe, whatever:ts size or material, and this hinders the flow of the water tosome extent. If it were not for the friction, the water wouldincrease indefini
. The principles underlying radio communication . sually abbreviatedto emf. The larger the number of cells which are joined inthe circuit in such a way that their pressures will add, thegreater the electric pressure in the circuit and the larger the-current produced, just as the rapidity of flow of the water inthe pipe line may be increased by increasing the pump pressure. 24 RADIO COMMUNICATION. Resistance.—There is always some friction in pipe, whatever:ts size or material, and this hinders the flow of the water tosome extent. If it were not for the friction, the water wouldincrease indefinitely in speed. Similarly, there is friction in theelectric circuit. This is called the resistance of the greater the resistance the smaller the current which can beproduced in the circuit by a given battery, just as the greaterthe friction the less rapid the flow of water with a given pumpacting. A resistance coil at any point in the circuit corre-sponds to a partially closed valve in the pipe at any point(Fig. 4.). FIG 4 FIG 5 FIG. lllu^trAtion of resiatAnoe byb&rtially closed vaIvc Water CircuitIllustrating Actionof Electric Condenp&r Alternating Water FlowIllustrating ElectricDisplacement Current. steady and Variable Currents.—If a pipe is connected to alarge reservoir of water maintained at the same level, the steadypressure of the constant head of water will cause a steady flowof water in the pipe. The quantity of water which will pass agiven point in one second will be the same at all times. Certainsources of electricity, such as batteries and some kinds of dyna-mos, produce an electromotive force which is practically con-stant, and will cause a practically constant current to flow incircuits to which they are connected. A steady electric currentIn one direction is called a direct current. In the case of the ordinary force pump, the water is given asuccession of pushes all in the same direction but separatedby intervals when the water is not being pushed.
Size: 2349px × 1064px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookpublisherwashi, bookyear1922
