A primary cell has an emf of 1.5V, when short circuited it gives a current of 3A. The internal resistance of the cell is:
Correct answer: C. 0.5 Ω
- A. 4.5 Ω
- B. 2 Ω
- C. 0.5 Ω
- D. 1/4.5 Ω
Explanation
The internal resistance of a cell can be calculated using the formula r = E/I, where E is the electromotive force (emf) and I is the current. In this case, the emf is 1.5V and the current is 3A when short-circuited. Therefore, the internal resistance r = 1.5V / 3A = 0.5 Ω. This is why option C is correct. Options A, B, and D provide incorrect calculations that do not match the given values.
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About Current Electricity
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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