The potential difference across the terminals of a battery of emf 12 V and internal resistance 2 Ω drops to 10 V when its is connected to a silver voltmeter. Find the silver deposited at the cathode in half an hour. Atomic weight of silver is 107.9 g mol–1.
Let the current through the circuit i be.
Emf of battery, E = 12 V
Voltage drop across the voltmeter, V = 10 V
Internal resistance of the battery, r = 2 Ω
Applying Kirchhoff’s Law, the algebraic sum of voltage and voltage drop in the circuit is zero,
we get
Where, E = battery emf
V=voltage drop
r=internal resistance
I = current through the circuit
Using the formula, from faraday’s law of electrolysis –
where,
m = the mass of the substance deposited on the electrode
z=electrochemical equivalence
i=current passing
t=time taken