A storage battery of EMF E = 12 V and internal resistance r = 1.0 Ω is being recharged by an external DC charger with a current of 2.0 A. What is the terminal potential difference (V) across the battery terminals during charging?
Answer and explanation
Correct answer: D. 14.0 V
- Step 1: When a cell is discharging, current leaves the positive terminal, and terminal voltage is: .
- Step 2: When a battery is being recharged by an external charger, current is forced into the positive terminal in the reverse direction.
- Step 3: In this charging mode, the internal resistance drop adds to the EMF: .
- Step 4: Substitute values: .
Answer
14.0 V
Why not the others: '10.0 V' uses the discharging formula (); '12.0 V' ignores internal resistance drop; '6.0 V' is half the EMF.
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