Electrical Circuit Lab PDF 2020-2021

First-class College of engineer AI Muthanna Un. Electrical Circuit Lab. By Dr. Moneer Ali Lilo 2020-2021 Electric Circuit Lab. First - class Introduction Component of AC lab. Resistance :- The electrical resistance of an object is a measure of its opposition to the flow of electric current. The reci...

First-class College of engineer AI Muthanna Un. Electrical Circuit Lab. By Dr. Moneer Ali Lilo 2020-2021 Electric Circuit Lab. First - class Introduction Component of AC lab. Resistance :- The electrical resistance of an object is a measure of its opposition to the flow of electric current. The reciprocal quantity is electrical conductance, and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω) A capacitor :- It is a device that stores electric charge in an electric field. It is passive electronic component with two terminals. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser. (a) (b) Figure 1: a) Many types of capacitor , b) The detail of the captor design 1 Electric Circuit Lab. First - class Figure 2: parallel and series conction of the capcitors An ideal capacitor is characterized by a single constant value for its capacitance. Capacitance is expressed as the ratio of the electric charge (Q) on each conductor to the potential difference (V) between them. The SI unit of capacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10−12 F), 1 µF (10−6 F) to about 1 mF (10−3 F). The unit utilizing to measure the capacitance value shown in table below:Prefix Name Abbreviation Weight Equivalent Farads Picofarad pF 10-12 0.000000000001 F Nanofarad nF 10-9 0.000000001 F Microfarad µF 10-6 0.000001 F Milifarad mF 10-3 0.001 F Kilofarad kF 103 1000 F The general form of the capctor is : Inductance: It is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the current, and follows any changes in current. From Faraday's law of induction, any change in magnetic field through a circuit induces an electromotive force (EMF) (voltage) in the conductors, a process known as electromagnetic induction. This induced voltage created by the changing current has the effect of opposing the change in current. 2 Electric Circuit Lab. First - class Figure 3: many typs of inductnce Types of Induction : There are two types of Induction self-induction and mutual induction. Mutual Induction The inductance of a coil due to current in another nearby coil is called mutual inductance. Self-Inductance The inductance of a coil or inductor due to its own current is called selfinductance. L = Ф/I L= Unit of Inductance The SI unit of inductance is Henry abbreviated as ‘H’. Where, 1 mH = 0.001 H. 1 μH = 0.000001 = 10⁻⁶ H. 1 nH = 0.000000001 = 10⁻⁹ H. 1 pH = 0.000000000001 = 10⁻¹² H 3 Electric Circuit Lab. First - class Exp.No.1 Tools for AC signal 1- Oscilloscope Theory:The oscilloscope is an instrument for analyzing of electrical circuits by observation of voltage waves. It may be used to study frequency, phase angle, and time, and to compare the relation between two variables directly on the display screen. Perhaps the greatest advantage of the oscilloscope is its ability to display the periodic waveforms being studied. Figure 1:- Oscilloscope Sinusoidal Power Sources:Any AC sinusoidal voltage (or current) shown in Fig.(1) can be define in following formula: ( ) ( ) where: 4 Electric Circuit Lab. First - class Figure 2:- illustrating for sinusoid signal attributes >>Vp is the peak amplitude ( amplitude of an AC waveform as measured from the center of the oscillation to the highest positive or lowest negative point on a graph). An amplitude measurement may be reported as peak, peak-to-peak, or RMS. >> Peak-to-peak amplitude is the total height of an AC waveform as measured from maximum positive to minimum negative peaks (the highest peak to the lowest valley) on a graph of the waveform. Often abbreviated as “P-P”, e.g., Vp-p or Vpp. >> In electronics, AC voltages typically are specified with a value equal to a DC voltage that is capable of doing the same amount of work. For sinusoidal voltages, this value is √ times the peak voltage (Vp) and is called the root mean square or rms voltage (Vrms), given by: √ >>The other important attribute for any sinusoidal signal its frequency which could be defined as number of cycle per second and measure in Hertz. Signal period could be defined as time needed to complete one cycle. 5 Electric Circuit Lab. First - class ( ) If period T=1sec → freq=1Hz ( ) T=1/5 sec → freq=5Hz From above figure it's obvious that signal period is reciprocal of its frequency >> Finally the phase shift between any two equal frequency signals ( ) 6 Electric Circuit Lab. First - class 2- Function generator Theory:A function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies. Some of the most common waveforms produced by the function generator are the sine wave, square wave, triangular wave and sawtooth shapes. These waveforms can be either repetitive or single-shot (which requires an internal or external trigger source) Figure 3: function generator This shows several waveforms: sine wave, square wave, triangle wave, and rising sawtooth wave. The fundamental frequencies of each waveform have the same frequency and phase, for comparison. Uses the data files and the gnuplot code in #Source code below Figure 4:- signals genrated by function genrator Sine, square, triangle, and sawtooth waveforms 7 Electric Circuit Lab. First - class Procedure 1- Use function generator to generate a sinusoidal signal with any amplitude and any frequency. 2- Apply the signal to the input terminals of the oscilloscope then measure peak voltage, Vp.p and period then sketch the signal. 3- Write the time equation for this signal. 4- Use AC voltmeter to measure RMS voltage then show if : 5- Use frequency meter to find signal frequency then show if: 8 Experiment no.3 R L C series circuits Object: To study the characteristics of ac circuits. Apparatus: 1- Dual beam oscilloscope. 2- Function generator. 3- Resistance box. 4- Capacitance box. 5- Inductance box. 6- Coaxial cable. 7- Connecting wires. Theory: A- Impedance: the impedance of a two terminal network may be expressed as: Z=v/I (ohms) Where z = complex impedance V= complex voltage I complex current The complex impedance is also expressed as: Z=r+jx in Cartesian form Z=zeiФ in polar form. The value of Ф can measure based on the value of the T and t , where, T is the period time of the wave, and t is the time shift between the signal on the resistance or the inductor as shown in the figure below. Phase angle in degree: scale. Where T, t is distance in any length Phase measuring using two channels of oscilloscope B- THE SERIES RC CIRCUIT: Fig 3.1 and fig 3.2 illustrated a series rc circuit connected to an ac voltage source. The applied voltage can be expressed as: V=Vm sinωt =Ir + ∫ 𝑖𝑑𝑡 The solution of this differential equation results in. I=IM sin(ωt+Ф) This equation shows that current I leads voltage v by Ф The impressed voltage v can expressed form as: V=VR - jVC Which can be expressed as (see phase diagram): |v|=√ √ =|I| √ Where XC=1/(ɷC) And the phase angle Ф is given by: Ф=tan-1(-VC/VR)=tan-1(-XC/R) Fig 3.1 : Circuit of series RC and wave form of the circuit Fig. 3.2 phasor diagram of series RC C- Series RL circuit: Fig.3.3 illustrate a series RL circuit to which a sinusoidal voltage is impressed. v=VM sin ωt Fig 3.3: circuit and waveforms Applying K.V.L, one gets: V=IR- Ldi/dt Solving that equation for I, one gets I=IM Sin(ɷt-Ф) Thus the current I lags the voltage v by Ф as shown in fig 3.4. From phase diagram, one express: |v|=√ √ =|I| √ Where XL= ωL Ф=tan-1(VL/VR)=tan-1(XL/R) Fig 3.4: Phasor diagram of a series RL circuit Procedure Part A: series RC circuit 1. Connect the circuit shown in fig 3.1 with (R= 100 Ω , 10 µ F) 2. Set the input voltage at 3VP.P, 300Hz 3. Measure the phase shift between the current I and the applied voltage v by using oscilloscope. Vp.p Freq. Draw the input signal Draw output signal on (R&C) Find phase angle Ф 4. Repeat all the previous steps with 3 Vp.p , 1KHz. Vp.p Freq. Draw the input signal Draw output signal on (R&C) Find phase angle Ф 5. Calculate the phase angle theoretically for the two cases Part B:series RL Circuit 1. Connect the circuit shown in fig.3.3 with (R=100 Ω, 10 mH) 2. Set input voltage at 3VP.P, 250Hz 3. Measure the phase shift between the current I and the applied voltage v by using oscilloscope. Vp.p Freq. Draw the input signal Draw output signal on (R&C) Find phase angle Ф 4. Repeat all the previous steps with 3 Vp.p , 1KHz. Vp.p Freq. Draw the input signal Draw output signal on (R&C) Find phase angle Ф 5. Calculate the phase angle theoretically for the two cases Discussion 1- Explain why the phasor and the impedance have the same angle. 2- Compare the result for utilized different frequency in same circuit for part A and B 3- At what condition the following results obtained? a- Phase angle equal zero b- The applied voltage lead the current by 90°. c- The average power equal to zero. 4- In general, how would the phasor diagram of Figure 3.2 change if the frequency was raised? 5- In general, how would the phasor diagram of Figure 3.4 change if the frequency was lowered? Experiment no. 4 R L C series circuits Object: To study the ac characteristics of RLC circuits. Apparatus: 1- Dual beam oscilloscope. 2- Function generator. 3- Resistance box. 4- Capacitance box. 5- Inductance box. 6- Coaxial cable. 7- Connecting wires. Theory: A- Impedance: the impedance of a two terminal network may be xpressed as: Z=v/I (ohms) Where z = complex impedance V= complex voltage I complex current The complex impedance is also expressed as: Z=r+jx in Cartesian form Z=zeiФ in polar form. A series RLC circuit is illustrated in fig.4.1. as obvious from the figure the effect of XL and XC are opposite. VL leads the current by 90° while VC lags the current by 90° thus the voltage across capacitor and inductor are out of phase by 180°. If the magnitude of these voltage are equal, they cancel each other and the total reactance in the circuit XL-XC=0 Fig.4.1: (a) circuit RLC in a series connection (b) phasor diagram of the RLC circuit The impedance shown in fig 4.2 of the circuit is Z=R+jXL-jXC Fig.4.2: impedance triangle of a series RLC circuit And the phase angle Ф shown in fig 4.2 is given by Ф=tan-1((VL-VC)/VR) =tan-1((XL-XC)/ R) If XL=XC the circuit is resistive XL>XC the circuit is inductive (lagging phase) XL