Continued from the preceding experiment, the effects of cold-work and annealing on the rigidity of copper wire are observed by the method of torsion pendulum. This time, cold-twisted copper wires are employed as the specimens. The results obtained are as follows. (Fig. 1). (1). From a certain annealing temperature T1', the rigidity becomes almost constant. (2). From another temperature T2', the rigidity decreases very rapidly. (3). The temperatures T1', T2' shift upward with the decrease of the degree of cold-work assigned to the specimens. From the above and previous results, the cause of the increase of rigidity of cold-drawn copper wire by low temperature annealing is discussed.
A new type pressure transducer for telemetric use is described. The twist of the free end of a spiral Bourdon tube is tranferred to the displacement of a movable coil placed between the poles of a C-shaped electric sheet steel core such as described in Report I. When the core is excited by an a. c. current, the amount of induced voltage in the coil tells the angle of twist of the Bourdon spiral. As a thermometer, the Bourdon spiral is filled with an appropriate liquid. As regards pressure, temperature, tidal current etc., fishes choose the surrounding conditions according to their kind to suit them. Hence, it will be of great help to' fishery if the underwater pressure and temperature can be measured correctly with the utmost ease. The apparatus described is designed for the purpose. It is kept in a stream-lined container to be towed underwater by a fishing boat. Wide field of application for remote control is in view.
It is very important to know about the grid temperature of transmitting tubes during exhaustion and operation. Measurements are made on 7T56, a water-cooled triode, by welding a fine Ta-W thermo-couple on to the middle portion of one of the side-rods with following results: (1) The inside surface of anode acts as a reflector. (2) The filament power and the equivalent grid dissipation are expressed as exponential functions of absolute temperature of the grid. (3) Influence of the anode temperature on the grid temperature is small. Approximate analyses are given on the above experimental results.