A galvanic cell converts chemical energy into electrical energy: the
anode (left, zinc) oxidises and loses electrons into the external wire,
while the cathode (right, copper/silver) reduces metal ions from
solution, gaining electrons. Ions cross the salt bridge to keep both
half-cells electrically neutral. Yellow spheres are electrons in the
wire; blue/grey spheres are metal cations drifting through the
electrolyte and salt bridge.
E_cell = Eยฐ_cathode โ Eยฐ_anode โ (RT/nF)ยทln(Q) (Nernst equation)
I = E_cell / (R_internal + R_external)
- Cell pair โ sets the standard potentials Eยฐ of each half-reaction; a bigger gap gives a bigger voltage.
- Electrolyte concentration โ shifts the reaction quotient Q, nudging voltage via the Nernst equation.
- External load โ resistance the current must push through; lower resistance means higher current for the same voltage.
- Temperature โ speeds up ion diffusion and reaction kinetics, raising current.