Bacis Electrical Circuit 1 DET 101/3 Bacis Electrical Circuit 1

List of text book and references 1. Charles K. Alexander & Matthew Sadiku, “Fundamental of Electric Cicuit”, International Edition, McGraw Hill,2001. References: 1. J.David Irwin & Chwan-Hwa WU,”Basic Engineering Circuit Analysis”,John Wiley & Son,7th edition,2001. 2. Nilsson,J.W. & Riedel, S.A,”Electric Circuit”,5th Edition, Addison Wesley,1996. 3. J.David Irwin,”Basic Engineering Circuit Analysis”,International Edition, 5th Edition, Prentice Hall, 1996.

GRADING THEORY ( 60%) PRACTICAL ( 40%) 1. Final Exam 50% 2. Test 1 & 2 10% PRACTICAL ( 40%) 1. Laboratory (7 modules) 30% 2. Lab Test 10%

Variables & Cct Elements International System of Units, SI Current and Voltage Power and Energy Ideal Basic Circuit Elements Basic Circuit Connections Application of Passive Sign Convention to Ohm’s Law and Power Calculation Kirchhoff’s Laws

Introduction There are several ways of describing or defining electric circuit: Definition 1: Electric circuit is a mathematical model that approximates the behavior of an actual electrical system. Hence the analysis of a circuit is a study of the behavior of the circuits. Definition 2: Electric circuit can be defined as an interconnection between components or electrical devices for the purpose of communicating or transferring energy from one point to another. The components of electric circuit are always referred to as circuit elements.

International System of Units (SI) Quantity Basic Unit Symbol Length Meter m Mass Kilogram kg Time Second s Electric current Ampere A Thermodynamic temperature Kelvin K Luminous intensity Candela cd

International System of Units (SI) Multiplier Prefix Symbol 1018 Exa E 1015 Peta P 1012 Tera T 109 Giga G 106 Mega M 103 Kilo k 102 Hector h 101 Deka da 10-1 Deci d 10-2 Centi 10-3 Mili m 10-6 Micro  10-9 Nano n 10-12 Pico p 10-15 Femto f 10-18 Atto a

Current and Voltage Figure 1.1: Two common types of signals constant or direct current/voltage. time-varying or alternating current/voltage.

Current and Voltage The electric current is the rate of change of charge over time, measured in amperes, A. Mathematically, current i, expressed in terms of charge, q and time, t is: i = dq/dt in coulomb/second or amperes.

Current and Voltage Voltage is defined as energy, w per unit charge, q created by the separation. Mathematically, we express this in differential form as: v = dw/dq in Joules/coulomb or volts

Power and Energy Reason why we should know about power and energy. 1st reason: Practically, any electrical devices have limitation in the power rating that they can handle. Exceeding the prescribed rating could destroy or make the device to malfunction. 2nd reason: We are paying our electrical bills to the power utility companies based on the amount of electric energy we consumed over a certain period of time. On top of all, we should realize that the useful output of our system is non-electrical form.

Power and Energy We define power as the time rate of expending (negative power) or absorbing (positive power) energy. P=dw/dt, in watts (W) The sign can be either positive or negative. +ve: The element is absorbing or dissipating (special case for a resistor) o or receiving power. -ve: The element is supplying or developing or expending or delivering or releasing power.

Ideal Basic Circuit Element Definition: Ideal – to imply that the element cannot exist as a realizable physical component. The purpose of its prescription is to model actual devices and systems. Basic – to imply that the circuit cannot be subdivided or further reduced into smaller parts.

Ideal Basic Circuit Element Types of Basic Circuit Element: Passive – elements are not capable of generating electrical energy. Resistor (dissipates energy) Capacitor and Inductor (can store or release energy) Active – elements capable of generating electrical energy. Voltage source Current source

Ideal Basic Circuit Element Linear resistor: Resistor is passive element that dissipates electrical energy. Linear resistor is the resistor that obeys Ohm’s law. Capacitor: Capacitor is passive element designed to store energy in its electric field. It is normally used in tuning circuits of radio receivers and s dynamic memory elements in computer systems.

Ideal Basic Circuit Element Inductor: Inductor is another passive element designed to store energy in its magnetic field. Its numerous applications can be found in electronic and power systems such as power supplies, transformers, radars and electric motors.

Ideal Basic Circuit Element Voltage source Independent source This source maintains a specified voltage between its terminals but has no control on the current passing through it. The symbol of the independent voltage source is a plus-minus sign enclosed by a circle.

Ideal Basic Circuit Element Dependent voltage source This kind of voltage source has a specified voltage between its terminals but it is dependable on some other variable defined somewhere in the circuit. The symbol for the dependent voltage source is a plus-minus sign enclosed by a diamond shape. The value of the dependent current source is KVx (dimensionless) or Kix (ohms) where K is the scale factor or gain.

Ideal Basic Circuit Element Current source Independent current source This source maintains a specified current through its terminals but has no control on the voltage across its terminals. The symbol of the independent current source is an arrow enclosed by a circle.

Ideal Basic Circuit Element Dependent current source This kind of current source has a specified current between its terminals but it is dependent on some other variable defined somewhere in the circuit. The symbol for the dependent current source is an arrow enclosed by a diamond shape. The value of the dependent current source is KVx (in Siemens) or Kix (dimensionless) where K is the scale factor or gain.

Kirchhoff’s Laws Kirchhoff’s Current Law Kirchhoff’s Current Law (KCL) states that the algebraic sum of current entering a node must be equal to that of leaving the same node. Applying KCL, we obtain; i2 + i6 = i1 + i3 + i4 + i5

Kirchhoff’s Laws Kirchhoff’s Voltage Law (KVL) Kirchhoff’s Voltage Law states that the algebraic sum of voltage drop in a loop must be equal to that of voltage rise in the same loop. Stated it in a different way is that the algebraic sum of all voltages around a loop must be zero. Applying KVL, we obtain; Loop 1: V1 + V2 + V3 = Vs Loop 2: V4 + VIs = V2