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LAB # 6
ALTERNATING CURRENT
CIRCUITS
PHY 156
Object of the Experiment and Theoretical Background
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View Full DocumentThe object of this experiment is to determine the effective value of the
current, rms current, in an RCL circuit. Also the resonance frequency and
phase relationships for instantaneous voltages in the series RLC circuit are
to be studied.
The effective value of the current is given by:
I
rms
=
V
rms
=
V
R² + ωL – 1
Z
ωC
The voltage across the resistor, inductor and capacitor has a different
amplitude and phase as can be seen in our graph 1. The voltage across the
resistor is in phase with the current, the voltage across the inductor leads the
current by 90º, and the voltage across the capacitor lags behind the current
by 90º. These phase relationships are useful to calculate the instantaneous
voltages across each component of the RLC circuit:
ΔV
R
= I
max
. R . sin(ωt) = ΔV
R
. sin(ωt)
ΔV
L
= I
max
. X
L
. sin(ωt + π/2) = ΔV
L
. cos(ωt)
ΔV
C
= I
max
. X
C
. sin(ωt  π/2) = ΔV
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 Spring '10
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 Current

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