For here the convection currents are small and the radiometer action has scarcely begun to be appreciable.
Between the Scylla of convection currents at higher pressures and the Charybdis of radiometeraction at lower pressures, there seems to be a channel at a pressure of about two or three centimetres of mercury.
His radiometer will turn in the light of day and in the darkness of the night; it will turn everywhere where there is heat, and heat is everywhere.
Instead of using the fan in this experiment, we may use the "electric" radiometer with similar effect.
In trying the preceding experiment with the electric radiometer the potential should not exceed a certain limit, as then the electrostatic attraction between the vanes and the glass of the bulb may be so great as to stop the rotation.
A Crookes electric radiometer is also spun around when connected to one of the terminals of the coil, but only at very high exhaustion or at ordinary pressures.
The radiometerhas already entered the field of industrial science, and is used to measure the duration of exposure of photographic plates.
The latest use to which the radiometer has been put was to test the viscosity of gases at decreasing pressures.
For washing out the radiometer with oxygen the arrangement shown in fig.
The radiometer and bulb B were heated, exhausted and repeatedly washed out with pure oxygen gas, and then the mercury was allowed to distil for some time into the charcoal cooled in liquid air.
Here A is a bulb containing perchlorate of potash, which when heated gives off pure oxygen; C is again the radiometerand B the charcoal bulb.
When, however, the mercury was warmed by placing the bulb in liquid water, the vanes began to move again, and in the particular radiometer used this was found to happen when the temperature of the mercury had risen to -23 deg.
When a similar radiometer was filled with hydrogen and the attached charcoal bulb was cooled in liquid air rotation took place, because sufficient of the gas was absorbed to permit motion.
The moving part of the radiometer is a small horizontal wheel, to the ends of whose arms are fastened vertical vanes, usually of mica, and blackened on one side.
In an atmosphere of ordinary density, the accession of heat which the vanes of a radiometer might receive from a radiant source would be diffused through the mass of the inclosed air.
Thus it appears that we have been able to show by very definite experimental evidence that the radiometer is a heat engine.
To avoid misapprehension, we may here add that, in orderto obtain in the radiometer a reaction between the heater and the cooler, it is not necessary that the space between them should actually be crossed by the moving molecules.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "radiometer" in a variety of sentences. We hope that you will now be able to make sentences using this word.
