AReS

PART1R, L, C Circuit

Experiment 13 :AC RC Circuit

Theory

The AC resistance of capacitor is X_C=-1/(2πfC), and X_C gets lower as the frequency of AC current flowing to the capacitor is high. All condensers of this characteristic has not only the AC resistance but also DC resistance which delays the energy charging and loss resistance which discharges the charged energy. Therefore, if AC resistance of capacitor is XC and DC resistance is R, the combined resistance of these is impedance and expressed as Z. The relationship between the current and the voltage follows Ohm’s law and the impedance Z and the phase can be expressed as below.

$Z = R - jX_C , ~~~Z = E over I , ~~~ PHI = {tan}^-1 ~-X_C over R$

fig1-21

Fig. 1-21Relationship of R-C Circuit and Phase

Fig.1-21 shows R-C serial circuit. The combined resistance(impedance) of R-C circuit becomes Z = √ R₂ + X_C². And the phase difference of voltage to current becomes as fig.(b), not 90°.

Experiment Process

fig1-22

Fig. 1-22C-R Circuit and Impedance(Z)

1. Connect as fig.1-22(a) the AC power to the left terminal of R8 and lower terminal of C2 of Block e in M01, change the frequency according to table 1-13, and measure E_C ,E_R and record the result in the relevant column. Calculate the impedance Z with the given formula and record the result.

tab1

Experiment 1-13.1 AC RC Circuit (Compose as in fig.1-22(a).)

1.Connection

1.Circuit Connection

Function Generator connection

Connect between A+ terminal of Signal Output on front panel and left terminal of R8 of Block e with red line, and between A- terminal and lower terminal of C2 with black line.

Voltmeter Connection

Connect between A+ terminal of Signal Input CH A on front panel and left terminal of R8 of Block e with red line, and between A- terminal and right terminal of R8 with black line.

Connect between B+ terminal of Signal Input CH B on front panel and upper terminal of C2(right terminal of R8) with red line, and between B- terminal and lower terminal of C2 with black line.

2.Wiring Diagram

flash

3.Measurement

1Choose analog output at left menu of front panel.
In Function Generator window, set up Amplitude as 20vpp, amplitude 50% , Frequency as 1k , Signal as sine and click on to output 1KHz 10Vp-p.
2Choose analog input at left menu of front panel.
Choose Volt & Ampere Meter tab and choose voltage, pp, ac at CH A and CH B, then the measured value is indicated. Record it in the relevant column of table 1-13. CH A is Ec value, and CH B is ER value.
3Choose analog output at left menu of front panel.
In Function Generator window, choose Frequency as 100 , click frequency 500hz to make 500Hz button_arrow and execute 2) process.

In Function Generator window, choose Frequency as 100 , click frequency 1.5khz to make 1500Hz button_arrow and execute 2) process.

In Function Generator window, choose Frequency as 100 , click frequency 2khz to make 2000Hz button_arrow and execute 2) process.
4After the measurement, click on red2 to cut off the output of function generator.

4.Calculation

1. In table 1-13, calculate the impedance Z with given formula and record the result.