Showing Rlc Circuit Resonance With Electronics Workbench

In circuit analysis courses, RLC circuit resonance is a topic that is difficult to teach without demonstration. The physical demonstration of this topic requires several kinds of circuit components and equipment. Some of these devices may not be available in a typical engineering or engineering technology department laboratory. This paper presents teaching RLC circuit resonance with Electronics Workbench [1], a popular circuit simulation software package. With Electronics Workbench, RLC circuit resonance can be demonstrated very easily. This software package can save both the cost of the circuit components and the time to build and modify the circuit. Using Electronics Workbench, students can change the circuit parameters to the values they want and find the voltages and currents of the circuit corresponding to these values. Therefore, they may see the conditions of RLC circuit resonance from the circuit simulation for themselves. Introduction For circuit analysis courses, RLC circuit resonance is a topic that is not easily accepted by students when they are taught in a classroom. RLC circuit resonance can be shown mathematically. For example, in a series RLC circuit the inductive reactance cancels out the capacitive reactance at resonant frequency. Therefore, the circuit has a minimum impedance and a maximum current at this frequency. However, it is hard to see from the formulas how the reactance and the current respond to the frequency change, when the circuit frequency is approaching the resonant frequency. It is also difficult to introduce the sensitivity of a RLC circuit and the effectiveness of the capacitance or the inductance to resonance or sensitivity. RLC circuit resonance can be demonstrated in a laboratory. The experimental demonstration can give students a chance to see this electrical phenomena. However, the equipment used in this demonstration is not always available in all college laboratories. Electronics Workbench, a computer circuit simulation software, has been used in many universities and technical schools. It has been used for beginning electrical engineering technology courses [2] and digital fundamental courses [3]. With Electronics Workbench, the maximum power transfer theorem and RLC circuit resonance can be demonstrated very well. Also, this does not require any laboratory equipment. P ge 260.1 Demonstrating Series RLC Circuit Resonance In a series RLC circuit, resonance occurs when the circuit’s capacitive reactance equals its inductive reactance. The applied voltage’s frequency, which causes resonance, is called resonant frequency. When a series RLC circuit is in resonance, the circuit has the following properties: (a) The impedance has its minimum value. (b) The current has its maximum value. (c) The voltage across the capacitor equals the voltage across the inductor. (d) The voltage across the resistor equals the applied voltage. (e) The phase angle between the current and the applied voltage is zero degrees. With Electronics Workbench, these properties can be used to locate a circuit’s resonant frequency or be proven when the resonant frequency is located. Let students build the circuit shown in Figure 1, where it is known that the resonant frequency of the circuit is not greater than one MHz. Therefore, the search range for the resonant frequency is from zero to one MHz. Because Electronics Workbench does not accept zero Hz of AC voltage, we may start from 0.001 Hz or any frequency that is close to zero Hz.