Unit 1.3 - Circuit Elements

# Unit 1.3 - Circuit Elements - AC and DC DC Direct Current...

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9/9/10 Dr. Bruce McCann 1 Basics Concepts and Laws Unit 1.3 Circuit Elements 2 AC and DC DC: Direct Current Electrical current that flows in one direction only. AC: Alternating Current Electrical current that changes (or alternates) in magnitude and direction at regular intervals. These terms are also applied to voltages: DC voltage or AC voltage • Direct Current Voltage may seem weird, but that’s the way it is. 3 EE302: DC Circuit Analysis Nomenclature: lower case i, v denote general representations for current and voltage that may be DC or AC. For EE302, we will focus on DC circuits I (upper case) will denote currents V (upper case) will denote voltages 4 Types of Devices Active Devices Capable of generating power Examples: voltage and current sources, operational amplifiers, transistors Passive Devices Cannot generate power Examples: resistors, capacitors, inductors For EE302, we focus on DC circuits involving resistors 5 Physical System Example #2 6 Schematic of Physical System

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9/9/10 Dr. Bruce McCann 2 7 Physical System Example 8 Diagram of Physical System 9 Headlight Circuit Diagram + - 12 V 10 The Basic Circuit Element It has only two terminals It is described mathematically in terms of current and voltage at those terminals. + i v 1 2 - Circuits are a collection of interconnected elements. Independent Sources 12 Ideal Voltage Source If supplying power to circuit, which way does the physical current flow? Always provides the specified voltage between its terminals. Current determined by the attached circuit. Can supply unlimited current. Can supply unlimited power. + - 12 V a b I I
Dr. Bruce McCann 3 13 Battery Voltage Source Source of power Provides voltage (12 V) Provides current • Varies depending on what is attached to the battery + - 12 V or Circuit Symbol: + - 12 V 14 Circuit Symbols for Voltage + - v(t) General Voltage Source + - 12 V DC Voltage Source + - 120 V ~ AC Voltage Source 15 Ideal Current Source Always provides the specified current flowing from b to a. Voltage determined by the attached circuit. Can provide unlimited voltage. Can provide unlimited power. 2 A a b No everyday analogy for a current source. Important for modeling more advanced devices. + V - 16 Circuit Symbols for Current 2A General Current Source DC Current Source i(t) 17 I-V Characteristics I V i = I s v = V s Ideal current source V s I s Ideal voltage source 18 Headlight Can I represent the headlight as a voltage or current source? No

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Unit 1.3 - Circuit Elements - AC and DC DC Direct Current...

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