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Step 1:

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The emf of the 10 primary cell $\"image\"$ is 15 V.

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The Load resistance connected across the cell $\"\"$ is $\"\"$ .

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The terminal potential difference $\"\"$ is 12 V.

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The voltage across the load is defined as $\"\"$ .

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Voltage across the load is equal to the potential difference across the terminal of the battery.

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$\"\"$

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$\"\"$

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The supplied current $\"\"$ .

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Step 2:

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Suppose that the battery with emf $\"image\"$ and internal resistance $\"image\"$ supplies a current $\"image\"$ through an external load resistor $\"image\"$ , then the potential difference across the battery is $\"\"$ .

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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The overall internal resistance is $\"\"$ . \ \

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Internal resistance per cell is $\"\"$ .

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Step 3:

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Power in the external circuit :

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Power can be calculated using the relation : $\"\"$ .

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Where $\"\"$ is emf of the battery, \ \

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$\"\"$ is current through the circuit,

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$\"\"$

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Therefore, the power in the external circuit is 6 W.

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Solution:

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The supplied current $\"\"$ .

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Internal resistance per cell is $\"\"$ .

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the power in the external circuit is 6 W.

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