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Electric Bell - Working Principle and Components
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An electric bell has a resistance of $5 \Omega$ and requires a current of $0.25\ A$ to work it. Assuming that the resistance of the bell wire is $1 \Omega$ per $15m$ and that the bell push is $90m$ distance from the bell. How many cells each of emf $1.4V$ and internal resistance $2 \Omega$, will be required to work the circuit.
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A
$5$
💡 Explanation:
Total resistance = R_bell + R_wire = 5 + (90/15)1 = 11 ohms. Current = 0.25A. Total EMF required = I * R_total = 0.25 * (11 + nr_internal). Solving for n with 1.4V cells.