1. Complete the chart by adjusting the values of frequency and measuring Ic and
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Question
1. Complete the chart by adjusting the values of frequency and measuring Ic and Vc using the Agilent Multi-meter and then from these values calculating the value of Xc in the last column. Note: Current is measured in series with the capacitor and voltage is measured in parallel (across) the capacitor. Capture screenshots showing the measured values of Ic and Vc using the Agilent Multi-meter. 2. Discuss the following: a. Describe the relationship between the frequency and the capacitive b. What effect does frequency have on Ic and Vc for a fixed value of c. For a frequency of 1000Hz, what would be the effect of increasing the d. Why is it necessary to measure current in series with a device and e. Why is it necessary to determine Xc from measured values of current reactance capacitance in this circuit? value of the capacitor on the current Ic and the voltage Vc? voltage across it? and voltage as opposed to measuring it directly with a digital multi- meter? (It may be helpful to perform research on the internet to gain more insight into the topic of this question.) Include all calculations, screenshot of measurements, the table results of part 2 and the answers to part 5 in a word processing document and submit as EE115W2LabYourGID.docx, or an equivalent word processing file extension.Explanation / Answer
Answer:-a) The capacitive reactance is inversely proportional to the frequency. The magnitude of capacitive reactance can be written as-
| XC | = (2*pi*f*C)-1 . Here C is capacitance of the capacitor. In actual XC is an imaginary term and is written as-
XC = (j*2*pi*f*C)-1 .
b) When frequency is zero, i.e DC supply is given to capacitor, capacitive reactance is infinity, thus current through capacitor is zero. At this time voltage across capacitor is maximum i.e the supply voltage.
When frequency starts increasing then capacitive reactance value starts decreasing and hence current flows through capacitor. Also voltage drop across capacitor starts decreasing.
c) If frequency is fixed to 1 kHz, and we are changing the capacitance of the capacitor then at low capacitance current will be less and voltage will be high, if capacitance value is increased then current increases and voltage decreses.
NOTE:- voltage has inverse relation with capacitance, but current has direct relation with capacitance.
d) Current is always measured in series with device because if we connect the ammeter across the device then current branches at the point of taping and we do not the current that is actually flowing through the device.
Voltage is always measured in parallel with device because parallely connected components have same voltage drop. So when voltmeter is connected parallely with capacitor then both, voltmeter and capacitor has same voltage drop and hence correct measurement is done.
e) As capacitive reactance is dependent on the frequency of the source, so we need to measure the capacitive reactance by measuring the voltage and current. Resistance of a resistor is independent from the frequency and is a real value whereas capacitive reactance is an imaginary value.
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