What is the impact of having a small cathode and a big anode?

The option indicating enhanced current efficiency is correct because a smaller cathode relative to a larger anode can help in concentrating the current flow over the cathode area. This leads to increased current density at the cathode, which can enhance the electrochemical reactions occurring there, such as the reduction processes that provide cathodic protection.

In this scenario, the smaller surface area of the cathode operates efficiently, ensuring that the protective measures are effective without wasting current on a larger surface area that doesn't require it. This arrangement allows for better utilization of the impressed current, making the cathodic protection system more effective.

In contrast, a larger anode could provide additional surface area to support these reactions but also contributes to higher resistance pathways in the system, potentially leading to reduced current efficiency. Therefore, the relationship between anode and cathode sizes has a significant impact on how effectively cathodic protection systems can function.