In separation techniques, electrophoresis separates primarily by which property?

• A. Size
• B. Charge
• C. Color
• D. Temperature

Answer: (B)

Electric fields move charged particles; in electrophoresis the key factor that determines how far and in what direction a molecule travels is its net electric charge. The driving force is the product qE, so molecules with greater net charge experience a stronger push toward the opposite electrode and migrate faster. The gel or buffer provides resistance, so size and shape influence how easily a molecule moves, adding a secondary effect, but the primary criterion that governs separation is the molecule’s charge. Neutral species do not migrate, while the charge determines direction (toward the opposite-charged electrode). Color or temperature do not set the migration pattern, so the essential reason this method separates substances is their net charge.