East West University Department Of Computer Science And Engineering Course

East West University Department of Computer Science and Engineering Course No: CSE 109 Expt No: 05 Familiarization with Alternating Current (AC) Waves OBJECTIVE: To study ac (sinusoidal) wave forms and correlate them with measured effective values. An understanding of a simple ac circuit is also expected to be developed in the experiment.

INTRODUCTION: Any periodic variation of current or voltage where the current (or voltage), when measured along any particular direction, goes positive as well as negative with zero average value over a period is defined to be an AC quantity. Sinusoidal AC wave shapes are the ones where the variation (current or voltage) is a sine function of time.

Fig 01. An ac (sinusoidal) voltage waveform For the wave form in Fig. 01, Time period Frequency, f

= =

T 1/T

ν

=

V sin 2πƒt = V sin (2π/T) t

Effective Value: Effective (rms) values of sinusoidal vaveforms are given as: V= These values are directly measured by ac voltmeter/ ammeters. Phase difference between two ac sinusoidal waveforms is the difference in electrical angle between two identical points f the two waves. In fig. 02, the voltage and current equations are given as: ν=V sin 2πƒt = V sin (2π/T) t

IMPEDANCE: Relation between the voltage across and the current through any component of an ac circuit is given by impedance. For the voltage and current waveforms in Fig. 02, the corresponding impedance Z is given as: Z=

EQUIPMENT:        

Oscilloscope Function Generator 100Ω resistance 1µF capacitance AC voltmeter AC ammeter Breadboard Connectors

CIRCUIT DIAGRAMS:

LAB PROCEDURE: 1. Connect the output of the function generator directly to channel 1 of the oscilloscope as shown in Fig 03. Select sinusoidal wave shape. Set the frequency of function generator at 1 kHz and the amplitude of the wave, so that the peak-topeak voltage is 10V. 2. Determine the amplitude, time period of the wave from the Oscillogram. Calculate the frequency and rms value of the signal. 3. Measure the voltage with an ac voltmeter. 4. Construct the circuit as shown in fig.04. Use the supply as shown in fig. 04. Measure the input voltage with an ac voltmeter and the input current with an ac ammeter. The ratio between the voltage and the current gives the magnitude of the impedance, Z. 5. Observe the shapes of oscilloscope channels 1 and 2 simultaneously. Determine the phase difference between the two waves. Also observe which of the two waves lead. The phase difference between signals of channel 1 and channel 2 is the impedance angle. 6. Measure the voltage across capacitance and resistance using voltmeter.

PRE-LAB WORK: 1. Calculate the impedance from the values of resistance and capacitance and the supply frequency shown in Fig. 04.

POST_LAB REPORT: 1. Compare the frequency of the wave determined from the oscilloscope in step 2 with the set value on the function generator. 2. Calculate the rms value of the voltage observed in step 2 and compare with the measured voltage in step 3. 3. Calculate the impedance value from the readings taken in step 5 and step 6.