Lecture 2: Circuit Elements & Schematics Nilsson ENG17 (Sec. 2): Circuits I Spring April 3, 2014

Overview Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 2

5 Ideal Basic Circuit Elements Voltage Sources Current Sources Resistors Inductors Capacitors 3

Ideal Sources 4 Voltage Source (const. voltage) Current Source (const. current)

Dependent Sources 5 Voltage Sources Current Sources

Schematics 6

Schematics (w/dependents) 7

Schematics - GND Ground (GND) is a common connection Typically connect to Earth GND Always a zero [V] reference potential 8

Overview Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 9

Ohm’s Law 10

Conductance 11

Power & Ohm’s Law 12 Therefore… Ohm’s Law Power Relationship

Examples 13

Overview Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 14

Designing a Circuit Model 15

Additional Elements 16 Short Circuit Open Circuit Switch

Schematic V9V

Overview Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 18

The Setup 19

Kirchhoff’s Current Law (KCL) 20 The algebraic sum of all the currents at any node in a circuit equals zero. Therefore: Assign signs to currents at each node Positive (+) for current leaving a node Negative (-) for current entering a node Or vice versa

Kirchhoff’s Voltage Law (KVL) 21 The algebraic sum of all the voltages around any closed path in a circuit equals zero. Therefore: Assign signs to voltages in a loop Positive (+) for voltage rise Negative (-) for voltage drop Or vice versa

Observations 7 equations  4 equations –Because I and V are related through R, we only need one With only 2 branches at a node (in series), we only need to know 1 current 22

KCL Example 23

KVL Example 24

Overview Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 25

Finding v o 26

Finding v o 27 KVL: KCL: Ohm’s Law:

Recap Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources 28