Overvoltage - Lead and Zinc in HCl
A zinc strip placed in hydrochloric acid generates gas bubbles, but a lead strip in the same solution does not. When the two metals touch, still no bubbles are generated at the lead strip. No gas is generated at the lead strip when the metals are separated in the solution but connected by an external wire, since lead's overvoltage is higher than zinc's overvoltage.
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