USCG Exam PracticeDC circuits and electronic principles
A lead-acid storage cell has a nominal open-circuit voltage of 2.1 V. A technician measures the same cell at 2.1 V on open circuit but finds it delivers very little current under load. What is the most likely cause?
- A. The cell's electrode chemistry has changed, lowering its rated voltage.
- ✓ The cell has high internal resistance, causing terminal voltage to sag under load.Correct
- C. The cell is a primary type and cannot sustain a discharge current.
- D. The electrolyte has increased the cell's amp-hour capacity, limiting current.
Why B is correct
NEETS Mod. 1 §2-1 states that internal resistance limits maximum current and causes terminal voltage to sag under heavy load; a cell with high internal resistance delivers little usable current even when its no-load voltage appears normal. Open-circuit voltage alone does not confirm a healthy cell.
Cited:NEETS Mod. 1 §2-1