
Topics
Points of Emphasis
Prerequisites
Lab Activities
Gives an overview of AC circuits. In particular, the following theoretical
predictions concerning AC circuits are checked by the student:

the current in a circuit and the voltage across a resistor are always "in
phase";

the current in a circuit leads the voltage across a capacitor by 90
degrees;

the current in a circuit lags behind the voltage across an inductor by 90
degrees;

the ratio of the voltage across a capacitor to the capacitive reactance,
1/wC, gives the current in that circuit element;

the ratio of the voltage across an inductor to the inductive reactance, wL,
gives the current in that circuit element;

for an LRC circuit with a square wave driving voltage:
a. when R < 2*(L/C)^{1/2}, the current oscillates with an angular frequency given
by w = (1/L*C)^{1/2};
b. when R = 2*(L/C)^{1/2}, the current does not oscillate but rather returns to
zero in the fastest possible time; and
c. when R > 2*(L/C)^{1/2}, the current does not oscillate but rather returns to
zero slower than the critically damped case.

for an LRC circuit with a sine wave driving voltage:
a. when w^{2} << the natural oscillating frequency squared, w_{o}^{2}, the current
leads the driving voltage by approximately 90 degrees;
b. when w^{2} = w_{o}^{2}, the current is in phase with the driving voltage; and
c. when w^{2} >> w_{o}^{2}, the current lags behind the driving voltage by
approximately 90 degrees;

a plot of the angular frequency of the driving voltage vs the current is
that of a typical resonance curve; and

the ratio of the driving voltage to the impedance gives the current in the
circuit.
Quantitative results tend to be within 10% of the theoretically predicted values.
Course Level
Introductory level  P4, P14, P16
Student Handouts
Equipment
Number of setups available: 20
Per lab station:
1 oscilloscope
1 function generator
1 frequency counter
1 multimeter
1 resistance substitution box
1 capacitance substitution box
1 inductor
8 banana leads


Notes

