In: Physics
A 55.4 ? resistor is connected in series with a 16.2 microF capacitor and a 60 Hz, 140 V source.
a) Find the current in the circuit. Answer in units of mA.
b) What is value of the inductor that must be inserted in the circuit to reduce the current to one half the previous current?
Answer in units of H.
The capacitive reactance is,
XC = 1/C = 1/2fC = 1/2(60)(16.2x10-6) = 165.786
The impidence is,
Z = [XC2 + R2]1/2 = [(165.786)2 + (55.4)2]1/2 = 174.7978
The current in the circuit is,
I = V/Z = 140 / 174.7978 = 0.8 A = 800 mA
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The new current is, I'= I /2 =0.8 /2 = 0.4 A
So, the current is,
I' = V / [R2 + [XL - XC]2]1/2
0.4 = 140 / [ [ (55.4)2+[XL -165.786]2]1/2
Solve for XL, and we get XL = 511.373
Hence, the inductance of the inductor is,
XL = 2fL
L = XL/2f = 511.373 / 2()(60) = 1.356 H