Damping of Galvanometer Needles. 5t>7 



Galvanometer-Circuit closed. Period 7*78 seconds. 



Decrement — 



W "» =1-126. H 2 =l-119, ||i =1126, ^ =1-122, 

 482 431 383 341 



•« =1-117. §25=1121, g =1-186, §11=1-115. fl? =1-125. 

 305 2/2 242 217 193 



(b) 566 S*=l'-ll». 459=1127, ??? =1-118. 



504 450 399 357 



f5Z=M20, 3 ± 9 =M22, » =1-116, ** =1-124, i?=M25. 

 319 284 254 226 201 



Mean of above values= 1*121. 



9 /543 

 Average decrement from observations (#)=*/ — — =1120. 



(b) = v/— =1-122' 



W \/ 201 



Mean decrement, 5=1*121. 

 X=log e ^=0114. 

 Ratio, */X=681. 



When the period was short, the spot of light moved too 

 quickly for mo to be able to read on both sides of the zero. 

 For the two cases in which the period was 2*66 and 3*65 

 seconds respectively, I accordingly observed successive swings 

 on the same side of the zero. We then have 



a a b cs 2 



Hence the values for \ are hardly so certain in these cases 

 as in those in which the period was longer, especially as the 

 spot of light moves so fast that it is more difficult to observe 

 the deflexions accurately. A specimen of the readings of 

 this type is given below. 



Galvanometer -Circuit open. Period 3*65 seconds. 



(Decrement) 2 — 



w m=^ g-™. g-»* S;-' 1 -"* != 1092 ' 



~| = l-090, S=ia01-, j^-1099, !-§= 1093 ' ^=1112, 

 loo lob lol loo 124 



W l=* g-«"* S-'« • «-»»• ffi-^- 



