A voltage of 100 V is applied between parallel-plate electrodes 1 mm apart. What is the electric field strength between them? (Assume a uniform field.)

Answer: C. 1×10⁵ V/m

In a uniform field E = V/d: 100 V/(1×10⁻³ m) = 1×10⁵ V/m (100 kV/m, or 0.1 V/µm). The field points from the higher-potential electrode to the lower one, and its strength is the rate at which potential falls with distance. A narrower gap gives a stronger field at the same voltage, so thin insulating films need care about breakdown even at low voltages.

• A. 100 V/m treats the gap as 1 without converting it to meters.
• B. 0.1 V/m multiplies voltage by spacing; the correct operation is division.
• C. Correct. 100 V/1 mm = 1×10⁵ V/m.