(a) Explain the principle of conservation of charge and its relationship to Kirchoff's laws. (6)

(b) The open-circuit voltage of a cell as measured by a voltmeter of 100 ohm resistance, was 1.5 V, and the p.d. when supplying current to a 10 ohm resistance was 1.25 V, measured by the same voltmeter. Determine the e.m.f and internal resistance of the cell. (10)