Which of the following tends to increase internal resistance in a battery?

The tendency of internal resistance in a battery to increase with lower reactant concentration is an important concept in electrochemistry. When the concentration of reactants decreases, there are fewer charged particles available in the electrolyte to participate in the electrochemical reactions. This results in a greater resistance to the flow of ions, which is critical for maintaining current within the battery.

As the ion mobility decreases due to lower concentrations, the overall resistance to current flow increases, leading to what is known as internal resistance. In other words, the current is impeded by the scarcity of reactants, which impacts the performance and efficiency of the battery.

Higher voltage generally does not contribute to internal resistance directly, as it pertains more to the potential difference provided by the battery rather than the resistive properties. Increased temperature typically leads to decreased internal resistance, as higher thermal energy allows ions to move more freely. More efficient materials are designed to have lower resistance and enhance electron and ion flow, further countering factors that lead to increased internal resistance. Therefore, among the choices given, lower reactant concentration is the correct factor that notably increases internal resistance in a battery.