ECEN 215, Principles of Electrical EngineeringDr. Mina RahimianLecture# 1 Date: 8/26/13Overview of Electrical Engineering Electrical Engineers design systems that have two main objectives:1. To gather, store, process and present information.2. To distribute, store and convert energy between various forms.Major Classifications:a) Communication systems generate, transmit and distribute information. Examples: telephone systems, radar systems, sattelite systems,..b) Computer systems process and store information in digital form. Examples: A typical modern automobile contains tens of special purpose computers. Many electronic devices, household appliances, chemical processes and railroad switching yards routinely controlled through computers.c) Signal processing systems transform signals and the information contained in them into a the useful form. Examples: Image processing, voice recognition, fault detection,... d) Power systems generate, transmit and distribute electric power. Electric power is generated in large quantity in power plants by nuclear, hydroelectric and thermal (coal-, oil-, or gas fired) generators. Power is transmitted and distributed across the country by transmition lines and power grid.e) Control systems gather information with sensors and use electrical energy to control a physical process.Examples: Temperature control in heating/cooling system, temperature, pressure and flow rate control in oil refinery, autopilot systems in airplanes,...All these branches have something in common which is Electric Circuit Theory.Fundamental ConceptsElectrical phenomena are defined based on the concept of electric charge.Charactrerictics of electric charge:1. Charge is bipolar.2. Charge exists in descrete quantities, which are the integral multiples of electronic charge. ( 1.6 x10 ^ -19 colulombs)3. Electrical effects are attributed to both separation of charge and charge in motion.Voltage is the energy per unit charge created by separation of positive and negative charges.Current is the rate of charge flow.Ex. The current flowing through an element isCalculate the charge entering the element from t=0 to t = 2 s.i : current in amperesq : charge in coulombst : time in sec.Passive sign convention ( or, Passive Reference Configuration): when the current enters through the positive terminal of an element, passive sign convention is satisfied. In this case, use a positive sign in any expression that relates the voltage to the current. Otherwise, use a negative sign.Ideal circuit element:1. It has only two terminals .2. It is described mathematically in terms of its voltage and current.3. It cannot be subdivided into other circuit elements.Ex. The total charge entering a terminal is q=10 -10e^-2t (mc). Find the current at t= 0. 5 s.Power and EnergyEx. Assuming a 20 V drop from terminal b to a, and a current of 4 A enters terminal b.Find the value of v, i and p for different polarity references.If P > 0, the circuit element absorbs power and if p < 0, the circuit element delivers power.In any circuit sum of the element powers must equal zero.Ex. The numerical values of voltages and currents are given in the table. Find the power of each