TItE laws of the forced convection of heat from small wires carrying a steady electric current and moving transversely through air have been studied a.t some length.* A research into the case of small wires moving transversely in water was carried out by Messrs. Harold Worthington and C. B. Malone, Jr., as a thesis towards the S.B. degree, at the Massachusetts Institute of Technology, in 1915, under the direction of the Electrical Engineering Research Division. The results obtained a,re here brieflv summarized.
The test wire was of platinum, No. 3 ยฐ A. W. G. (o.256 ram. dianleter), supported in a vertical frame holder. The latter was carried on the end of a motor-driven rotating arm in such a manner that the test wire was dragged through the w a,ter o.f a large tank, in a direction transverse to its length, at an adjustable velocity, and at a constant depth of immersion. The vertical fr,ame was of steel, 4I cm. high, and designed so as to grip the test wire tightly, and to keep the latter vertically stretched, while stirring up the water as little as possible in the path of the wire's motion. The test wire was about 2o era. long, and was connected by the grips of the holder to a storage battery through a controlling resistance and ammeter. In this way the current I, through the test wire, could be carried up to 17 amp6res, under adjustable control. Pressure wires, fastened to the test wire, and 12.8 cm. apart, were led to a voltmeter, so as to show the drop of potential I 7 in this working portion of the test wire. The product 171 of the observed voltage and current gave the power dissipated by the wire, in watts, and this, divided bv I2.8. gave the linear power dissipation in watts per linear centimetre of the test wire. The ratio 17/I also indicated the working resistance of the 12.8 cm. of wire, and from this the mean temperature of the test wire became known.
* Communicated by the Director.