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#### Lab Activities

Gives an overview of AC circuits. In particular, the following theoretical predictions concerning AC circuits are checked by the student:

1. the current in a circuit and the voltage across a resistor are always "in phase";
2. the current in a circuit leads the voltage across a capacitor by 90 degrees;
3. the current in a circuit lags behind the voltage across an inductor by 90 degrees;
4. the ratio of the voltage across a capacitor to the capacitive reactance, 1/wC, gives the current in that circuit element;
5. the ratio of the voltage across an inductor to the inductive reactance, wL, gives the current in that circuit element;
6. 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.

7. for an LRC circuit with a sine wave driving voltage:

a. when w2 << the natural oscillating frequency squared, wo2, the current leads the driving voltage by approximately 90 degrees;

b. when w2 = wo2, the current is in phase with the driving voltage; and

c. when w2 >> wo2, the current lags behind the driving voltage by approximately 90 degrees;

8. a plot of the angular frequency of the driving voltage vs the current is that of a typical resonance curve; and
9. 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

#### Equipment

 Number of set-ups 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

 Last Update: Site contact: largent@Dartmouth.EDU