A dry cell delivering 2 A has a terminal voltage of 1.41V. What is the internal resistance of the cell if its open-circuit voltage is 1.59 V?
Correct answer: D. 0.09 Ω
- A. 5.09 Ω
- B. 6.09 Ω
- C. 7.09 Ω
- D. 0.09 Ω
Explanation
The relationship between EMF (E), terminal voltage (V), current (I), and internal resistance (r) is V = E - Ir. Rearranging for r gives r = (E - V) / I. So, r = (1.59 V - 1.41 V) / 2 A = 0.09 Ω.
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Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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