Which of the following statements is NOT true?

Analyze the question: We need the one statement that is false about cells and accumulators.

Check each option:

• A. A lead-acid accumulator can deliver a large current because of its very large internal resistance. This is false. A lead-acid accumulator has a very low internal resistance, which is why it can deliver a large current (for example, to start a car engine). From I = E/(R + r), a small r allows a large I. A large internal resistance would limit the current.
• B. A secondary cell can be recharged. This is true. The chemical reactions in a secondary cell are reversible.
• C. As a lead-acid accumulator is charged, the density of the acid increases. This is true. Charging converts lead sulphate back into lead, lead(IV) oxide and sulphuric acid, so the acid concentration and relative density rise. This is why a hydrometer is used to test the state of charge.
• D. The chemical action in a primary cell is irreversible. This is true, so primary cells cannot be recharged effectively.
• E. Conventional current flows from the positive to the negative terminal through the external circuit. This is true. (The wording "rlows" is a typo for "flows".)

Answer: Only A is false, so it is the statement that is NOT true.

Tip: In "NOT true" questions, test each option separately. Remember that accumulators have low internal resistance, and that is why they give large currents. Also remember that charging increases acid density, while discharging decreases it.