Electric Cells: Evaluating Statements on EMF and Properties
This solution evaluates the provided statements regarding electric cells to identify the correct one.
Statement Analysis
- Option 1: A primary cell is rechargeable.
This statement is incorrect. Primary cells, like dry cells or alkaline batteries, are designed for single use and cannot be recharged once depleted. - Option 2: A secondary cell can be used only once.
This statement is incorrect. Secondary cells, such as lithium-ion or lead-acid batteries, are designed to be recharged and reused multiple times. - Option 3: The emf of a battery is the power provided by the battery per unit current.
This statement is correct. Electromotive force (EMF), denoted as \(\mathcal{E}\), represents the total energy supplied by the cell per unit charge. It can be expressed as the ratio of power (\(P\)) delivered to the current (\(I\)) flowing through the circuit:\(\mathcal{E} = \frac{P}{I}\)
The unit of EMF is the Volt (V), which is equivalent to Joules per Coulomb (J/C). - Option 4: The unit of emf is Joule.
This statement is incorrect. The standard unit for EMF is the Volt (V). A Joule (J) is a unit of energy or work, while EMF is potential difference per unit charge. Specifically, 1 Volt = 1 Joule per Coulomb (\(1 \, V = 1 \, J/C\)).
Conclusion
Based on the analysis, the only correct statement is that the emf of a battery is the power provided by the battery per unit current.
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