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Series Circuits With Resistance and CapacitanceAuthor: E.E. Kimberly In the circuit of Fig. 515 the same current flows in both the resistance and the reactance. The resistance voltage drop is in phase with the current, and the capacitive reactance voltage drop lags the current by 90°, as indicated in Fig. 516. The angle 0 is the characteristic angle.
Example 57.  A resistor with R = 30 ohms is connected in series with a .condenser with C = 50 microfarads to a 220volt line whose frequency is 60 cycles. How much current will flow?
Solution.  The capacitive reactance is
The current is found as follows:
Example 58.  A resistor whose resistance is 10 ohms has a maximum safe current capacity of 5 amperes. It is to be used on a 220volt, 60cycle line in series with a condenser. What must be the capacitance of the condenser to limit the current to a safe value?
Solution.  The impedance is But Therefore, from which C = 0.000061 farad or 61 microfarads


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