Question

7. Three resistances of 2 ohm 4 ohmand 6ohm are connected
in parallel. What resistance must be connected in
series with this combination so that the total resistance
of whole combination is 10 ? [Ans. 8.9 ]​

Answer 1

Answer:

⛄Resistance in Series

$R \: series = R1 + R2 + .... + Rn \\ \\ R \: series = 2 + 4 + 6 = 12 \: ohm$

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⛄Resistance in Parallel

$\frac{1}{R} parallel = \frac{1}{R1} + \frac{1}{R2} + .... + \frac{1}{Rn} \\ \\ \frac{1}{R} parallel = \frac{1}{2} + \frac{1}{4} + \frac{1}{6} \\ \\ \frac{1}{R} parallel = \frac{3 + 6 + 2}{12} = \frac{11}{12} \\ \\ R \: parallel = \frac{12}{11} ohm$

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