The thermal G G detectors are especially useful for the purpose of quantitative measurements, because they indicate the true effective or square root of mean square value of the current or train of oscillations passing through the hot wire.
If all molecules moved with the velocity of mean square, the line would be drawn out into a band having on the frequency scale a width 2Nv/V, where v is now the velocity of mean square.
If the motion were that of a body at white heat, or say a temperature of loco, the velocity of mean square would be 39co metres per second and the apparent width of the band would be doubled.
In the case of an axial moment, the square root of the resulting mean square is called the radius of gyration of the system about the axis in question.
The mass-centre is accordingly that point the mean square of whose distances from the several particles is least.
