ox THE MEASTTREMEXT OF MAr4XETTC HYSTERE8TS. 
Gl 
we desired to damp the more violent motions of the coil, Rj, was diminished so 
that a current of 1/20,000 ampere could be sent through the suspended coil, the 
key Kg being opened to prevent any of this stronger current from j)assing round 
the secondary coil and affecting the magnetisation of the specimen. The final 
damping was always done with Kg closed and Rj, at its large value. We verified by 
experiment that currents many times larger than those actually employed for this 
purpose had no appreciable effect upon the hysteresis of the specimen. 
When the dynamometer is to be standardised the resistance coil X is taken out of 
the circuit and the eai'th-inductor is put in its place. 
Fracticcd Example of the Method. 
§ 36. To illustrate the working of the method, we now give a set of observations 
made to determine the hysteresis loss, W, as well as the mean maximum induction 
Bq, for a definite range of magnetic force RHq, for a specimen of soft iron :— 
Area of cross-section (circular) . . . . A = T78 sq. centim. 
Chan£>’e of Induction due to earth inductor P = 87200. 
Magnetic force j)er unit C.G.S. current . 47rN = 212‘2. 
Maximum current. = ’0706 C.G.S. 
Maximum magnetic force. Hq = 15. 
Number of turns on secondary coil ... m = 25. 
Throw of galvanometer due to eartli 
inductor. 8 = 12‘73 centims. 
Mean throw on reversing primary current = 15’63 centims. 
Mean maximum induction Bq = — 770^8 = 12030. 
Current when earth inductor is turned 
Throw of dynamometer due to earth 
inductor. 
Number of turns on secondary coil. 
Resistance of secondary circuit . . . . 
Length of secondary coil. 
Mean area of one turn of secondary coil . 
Throw, H from -f 15 to — 15 (E = 8 volts) 
Throw, H from — 15 to + I 5 (E = 8 volts) 
C' = -0527 C.G.S. 
cf) = 4‘68 centims. 
n = 300. 
S = 43 ohms. 
I = G-6 centims. 
G = '65 sq. centim. = 3’66A. 
dj = 23'85 centims. 
do = 23'30 centims. 
Hence U = 
CTX 
Ancf) 
(dj 4- do) = 311 ’8 (d^ + do) = 14700 ergs per cub. centim. per cycle. 
