eeng2009lec1 - EENG2009 Introduction to Circuits and...

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EENG2009 FS 2006 Part 1: Charge, etc. EENG2009 Introduction to Circuits and Electronics Part 1: Charge, Current, Voltage, Energy, Power, Sources 2.1 Major Topics of the Course 2.2 Circuits Quantities 2.3 Charge 2.4 Current 2.5 Voltage 2.6 Energy and Power 2.7 Practical Examples 2.8 Independent & Dependent Sources EENG2009 FS 2006 Part 1: Charge, etc. 2.1 Major Topics of the Course: 1. Basics, DC Analysis Techniques 2. Capacitors, Inductors, and Transient Analysis Techniques 3. AC Circuits, AC Power, Transformers, and Three-Phase 4. Semiconductors, Diodes, Op Amplifiers, and Power Supplies
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EENG2009 FS 2006 Part 1: Charge, etc. 2.2 Fundamental Circuits Quantities q (charge: coulombs, C ) i (current: amperes, A ) v (voltage: volts, V ) w (energy: joules, J ) p (power: watts, W ) S complex power: volt-amps, VA , watts, W volt-amps-reactive, VAR f (frequency: hertz, Hz ) EENG2009 FS 2006 Part 1: Charge, etc. 2.3 Charge When you rub a comb with a woolen cloth, a negative charge is produced on the comb and a positive charge is produced on the cloth . (Benjamin Franklin defined the charge on the comb as negative .) The comb acquires its negative charge because some of the electrons on the cloth are rubbed off onto the comb . One coulomb is defined as the amount of charge on identically charged particles, separated by one meter in a vacuum, that repel each other with a force of 10 –7 c 2 N , where c is the velocity of light (2.997… x 10 8 m/s). Recall that a single electron charge is –1.602 x 10 –19 C. This is quite small: For example, the charge needed to plate 1 g of copper is 3,036 C.
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EENG2009 FS 2006 Part 1: Charge, etc. 2.4 Current Charge in motion results in energy transfer. Of special interest is the case where the motion is confined to a definite path. In this case, current “flows.” Current is the movement of electrical charge—the flow of electrons through an electronic circuit. Current (i) is the rate at which charge “flows,” or is transferred. 1 amp = 1 coulomb/second It is convenient to think of current as the flowing motion of positive charge even though we know that current flow in metallic conductors results from electron motion (that is, the charge carriers are negative and move in the opposite direction.) i = dq/dt amperes Memorize me!! EENG2009 FS 2006 Part 1: Charge, etc. Charge/Current Relationship ++ + + + + + + The charge and the current flow through the conductor, passing from one side of the imaginary surface to the other. During the time interval from t a to t b the charge passing through the imaginary surface is i(t) i(t) Memorize me!! b a t t idt q =
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EENG2009 FS 2006 Part 1: Charge, etc. In defining current, both an arrow and a symbol are required. It takes two! Example: Circuit analysis shows that in the given circuit, i 1 has the value 0.5 A. Give the corresponding physical interpretation. 1 V 10 Ω 10 Ω 5 Ω 12 V i 1 = 0.5 A Solution: Since i 1 is 0.5 A, this means that 0.5 A, or 0.5 C/s is flowing in the direction of the current- reference arrow. This current flows through the 5 Ω , to the + side of the battery, through the battery, exiting from the – side of the battery.
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This note was uploaded on 06/01/2008 for the course COMPUTER E 203 taught by Professor Uzengil during the Spring '08 term at Jefferson College of Health Sciences.

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eeng2009lec1 - EENG2009 Introduction to Circuits and...

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