How do electrode size and spacing influence current density and treatment outcomes?

• A. Larger electrodes increase current density and focus the dose.
• B. Larger electrodes reduce current density and spread the dose; smaller electrodes concentrate current; spacing affects coverage and depth.
• C. Electrode spacing has no effect on depth.
• D. Electrode size only affects comfort, not dose.

Answer: (B)

The main idea is that electrode size and spacing shape the electric field by changing current density and the path the current takes through tissue. A larger electrode spreads the same current over a bigger area, lowering the current density at the skin and producing a more diffuse, less intense dose that covers a wider area. A smaller electrode concentrates the current into a smaller area, increasing current density and creating a more focal, stronger effect in targeted tissues. Electrode spacing alters the field’s path: when electrodes are farther apart, the current travels through more tissue and tends to reach deeper structures; when they’re closer together, the field is more superficial and localized. So, larger electrodes reduce density and spread the dose, smaller electrodes concentrate current, and spacing influences both coverage and depth of penetration.