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AP Physics C Chapter 31
1.
Test
Due 05/6/2011
A coil has a reactance of 1.55 k and draws 26 mA from an AC generator with a
terminal voltage of 60 V effective. What is its resistance?
RL = ___________
2.
A circuit consists of a capacitor with a reactance of 2500  in series with an
inductor of negligible resistance and a reactance of 2000 . What is the impedance
of the circuit?
Z = ________
3.
A little radio has a tuning circuit consisting of a variable capacitor and an antenna
coil. If the circuit has a maximum current when C = 300 pF and f = 40.0 kHz, what
is the inductance of the coil?
L = _______
4.
A 400-mH inductor with negligible resistance and a 185- resistor are in series
across a 60-Hz sinusoidal source. If the voltage drop across the resistor is 370 V,
what is the voltage across the inductor? What is the voltage across the AC source?
VL = ________
Vsource = _______
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AP Physics C Chapter 31
Test
Due 05/6/2011
5.
The input line to a transformer has an AC voltage of V in = 1100 V. If the primary
has Np = 100 turns, how many turns (Ns) should the secondary have if the output
voltage Vout is to be 550 V?
6.
A load resistor is placed across the secondary terminal of a step-down transformer
with a turn ratio of 4:1. IF the primary voltage and current are 120 V and 1.0 A
respectively, what will be the secondary voltage and current? Assume 100%
efficiency for the transformer.
7.
An AC transmission line transfers energy at the rate Pavg = 5.0 MW from a
generating plant to a factory.
a) What current irms is present in the line if the transmission voltage Vrms is 120 V?
b) If Vrms = 80 kV?
c) What is the ratio of the thermal (Joule) energy losses in the line for these two
cases? (Yes the joule heating loss in the line depends on the resistance in the
line, but you don’t need to know what the resistance is to answer the question.)
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AP Physics C Chapter 31
Test
Due 05/6/2011
8.A sinusoidal signal V(t)=Vmsin(t) is produced by an AC source and put across a
diode-resistor combination as shown in
the figure. In terms of Vm, compute the
following: the average value of the input
voltage (Vin, avg), the rms value of the
input voltage (Vin, rms), the average value
of the output voltage (Vout,avg), and the
rms value the output voltage (Vout,rms).
Vin,avg = _______
Vin,rms = _______
Vout,avg = ___________
Vout,rms = ___________
9
A series LCR circuit has inductance L in Henrys,
resistance R in ohms, and capacitance C in Farads.
An AC voltage of amplitude V0 is placed across the
circuit.
a) For what frequency f will the current in the circuit
be a maximum?
f max = _______________
b) What will be the value of the maximum current?
f min = ___________ _________________
c) For what frequencies with the current be one-half its maximum value?
f 1/2 = ____________ _______________
d) For what frequencies will the current be a minimum?
f min = __________ ______________
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AP Physics C Chapter 31
Test
Due 05/6/2011
10. AC voltage with amplitude V0 is applied
across a parallel LCR circuit as shown.
a) For what frequency is the current in the
capacitance C the same magnitude as
the current in the inductance L?
b) For what frequency is the current
through the AC source a maximum? A
minimum?
c) For what frequencies is the current
through the AC source twice the
minimum value?
11. A transformer has 500 primary turns and 10 secondary turns. (a) If V1,rms for the
primary is 120 V, what is V2,rms for the secondary, assuming an open circuit on the
secondary? (b) If the secondary has a resistive load R of 15 W, what are i1,rms and
i2,rms? Assume the transformer is ideal with no efficiency losses.
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