416 PROBLEMS AND EXERCISES. 



only required to be turned through 9. Compare the strength 

 of the current in the first case with that in the second case 

 when flowing through the thin wires which offered considerable 

 resistance. Ans. Currents are as I to -J-, or as 6 to I. 



-'"I I . A plate of zinc and a plate of copper are respectively 

 united by copper wires to the two screws of a galvanometer. 

 They were then dipped side by side into a glass containing 

 dilute sulphuric acid. The galvanometer needle at first showed 

 a deflection of 28, but five minutes later the "deflection had 

 fallen to ll. How do you account for this falling off? 



12. Classify liquids according to their power of conducting 

 electricity. 



13. Name the substances produced at the anode and kathode 

 respectively during the electrolysis of the following substances : 

 Water, dilute sulphuric acid, sulphate of copper (dissolved in 

 water), hydrochloric acid (strong), iodide of potassium (dissolved 

 in water), chloride of tin (fused). 



14. A current is sent through three electrolytic cells, the first 

 containing acidulated water, the second sulphate of copper, the 

 third contains a solution of silver in cyanide of potassium. How 

 much copper will have been deposited in the second cell while 

 2 '268 grammes of silver have been deposited in the third cell? 

 And what volume of mixed gases will have been given off at the 

 same time in the first cell ? 



Ans. '6614 grammes of copper and 332*8 cubic centi- 

 metres of mixed gases. 



15. A current passes by platinum electrodes through three 

 cells, the first containing a solution of blue vitriol (cupric 

 sulphate), the second containing a solution of green vitriol 

 (ferrous sulphate), the third containing a solution of ferric 

 chloride. State the amounts of the different substances evolved 

 at each electrode by the passage of 1000 webers of electricity. 



Am. First cdl, \ *?**? Atf > S^mmes of oxygen gas. 



( Kathode '3307 grammes of copper. 

 Second etO, Anode -0840 grammes of oxygen. 



( Kathode '2940 grammes of iron. 

 Third cell \ Anode '3727 grammes of chlorine. 

 ' \ Kathode '1470 grammes of iron. 



1 6. A tangent galvanometer, whose "constant" in absolute 

 units was croSo, was joined in circuit with a battery and an 



