d in series with the coil if the power input to the latter is to remain unchanged and t
1. An impedance coil takes 144 watts at a lagging power factor of 0.6. What value of capacitance
and resistance should be connected in series with the coil if the power input to the latter is to
remain unchanged and the overall power factor is to be unity (in resonance)? The circuit is
energized by a 120 volt, 60 cps source.
2. A series RLC circuit has a Q of 75 and a pass band between half-power frequencies of 160 cps.
Calculate the frequency of resonance and upper and lower frequencies of the pass band.
3. An impedance coil having a resistance of 30 ohms and a 50 cps inductive reactance of 33.3 ohms
is connected to a 125 volt 60 cps source. A series circuit consisting of a 20 ohm resistor and a
variable capacitor is then connected in parallel with the coil. (a) for what values of capacitance
will the circuit be in resonance? (b) calculate the two values of line current for the condition of
resonance.
4. A parallel-series filter like that of Fig. 13.10b in the scanned copy of the on page 364 is to be
designed to pass a wave having a frequency of 3500 cps and block a 2500 cps wave. The series
inductor has an inductance of 0.0023 henry. Calculate the capacitance of the series capacitor
and the parallel inductor.
5. A 15.9 uF capacitor and a 15.1 mH inductor are connected in parallel. In series with these units
are a variable resistor R and an adjustable device X, joined in series. (a) Determine the kind and
size of device X (inductance in Henry or capacitance in Farad) when the circuit is connected to a
50 volt 400 cps source and is adjusted to resonance. (b) For the resonant condition, calculate
the value of R if the voltage drop across the paralleled units is to be 100 volts.
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