Download Session 25 Answers - Iowa State University

Leader: Garrett Schieber
Course: Phys 222
Instructor: Dr. Al-Saqer
Supplemental Instruction
Date: 10/27/14
Iowa State University
1) The voltage across the terminals of an ac power supply varies with time according to
. The voltage amplitude is V0 = 46.0 V. (Book 31.3)
a) What is the root-mean-square potential difference Vrms?
Session 25: RLC Circuits
and Power
b) What is the average potential difference Vave between the two terminals of the power
supply?
2) In a series L-R-C circuit, the components have the following values: L= 20.0 mH, C= 140nF,
and R= 350 Ω. The generator has an rms voltage of 120 V and a frequency of 1.25 kHz.
(Book 31.26)
a) Determine the average power supplied by the generator
b) Determine the average power dissipated in the resistor
3) An ac source whose rms voltage is 80 V is in series with a 100- ohm resistor and a capacitor,
whose reactance is 200 ohms at the frequency of the source. The instantaneous current, when
the voltage of the source is zero and is increasing, is closest to:
a) Zero
b) 0.23 A
c) 0.16 A
d) 0.45 A
e) 0.32 A
Supplemental Instruction
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4) An R-L-C series circuit is constructed using a 175-ohm resistor, a 12.5-µF capacitor, and an
8.00-mH inductor, all connected across an ac source having a variable frequency and a
voltage amplitude of 25.0 V.
a) At what angular frequency will the impedance be smallest?
b) What is the impedance at this frequency?
c) At the angular frequency in part A, what is the maximum current through the inductor?
d) At the angular frequency in part A, find the potential difference across the ac source, the
resistor, the capacitor, and the inductor at the instant that the current is equal to one-half
its greatest positive value.
5) A transformer connected to a 120-V(rms) ac line is to supply 13000 V(rms) for a neon sign.
To reduce shock hazard, a fuse is to be inserted in the primary circuit; the fuse is to blow
when the rms current in the secondary circuit exceeds 8.50 mA. (Book 31.38)
a) What is the ratio of secondary to primary turns of the transformer?
b) What power must be supplied to the transformer when the rms secondary current is 8.50
mA?
c) What current rating should the fuse in the primary circuit have?