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Seven capacitors each of capacitance `2muF` are to be connected in a configuration to obtain an effective capacitance of `(10/11)muF`. Which of the combination (s) shown in figure will achieve the desired result? |
Answer» Suppose a parallel combition of n capacitors is connected in series with a series with a series combition of `(7-n)` capacitors. Capacitance of paralllel combination, `C_(1) = 2n muF` Capacitance at `(7-n)` series, and `C_(s) = (10)/(11) muF`, therefore, form `(1)/(C_(s)) = (1)/(C_(1)) + (1)/(C_(2)) + (1)/(2n) + (7-n)/(2) = (11)/(10)` Multiplying both sides by 10n, we get `5+5n (7-n) = 11n` `5+35n-5 n^(2) = 11n` or `5 n^(2) - 24n - 5 = 0` `(n-5) (5n + 1) = 0` Rejecting parallel combination of 5 capacitors must be connected in series with combination of 2 capacitors. |
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