OF ARTS AND SCIENCES. 307 



R 



.4776 



.5040 



.5280 



.5520 



.5592 



.6216 Ro 



.624 



.6264 



R /2 



See the curve representing the resistance in this experiment. There 

 is a great and rapid change in the resistance when the wire has been 

 stretched 20 centimetres. 



I _ L81_ _ ^ R _4776 



/o- 2.055 ~ ■'^^■^ Ro — 6'2r6 ''^^^ 



R P 



Here at this point 75- < y-o 



J^n 'o 



o 



Experiment 4. — In this experiment I used thicker copper wire, 



with the follovvino;' results : — 



.822 



I tried the same kind of wire again. It stretched considerably 

 before there was any change in the resistance. The origuial length 

 was l.fio metres. The final length was 1.82 metres. 23 lbs. broke the 

 wire before I had time to observe the resistance ; but, before Mp|)]ying 

 the last pound, the resistance was .076 ohms. The original re.sistance 

 was .072. 



Experiment 4b was with the same kind of wire, with these re- 

 sults : — 



