How many identical 1.5 V dry cells, each having an internal resistance r = 0.5 Ω, must be connected in series to establish a current of 1.0 A through an external load resistance R = 10 Ω?
Answer and explanation
Correct answer: C. 10 cells
- Step 1: For identical cells connected in series, total EMF is , and total internal resistance is .
- Step 2: Total circuit resistance is .
- Step 3: The circuit current is given by: .
- Step 4: Substitute : .
- Step 5: Rearranging: .
Answer
10 cells
Why not the others: '5 cells' yields ; '20 cells' yields ; '15 cells' yields .
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