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Lecture 2: Circuit Elements & Schematics Nilsson 2.1-2.5. ENG17 (Sec. 2): Circuits I Spring 2014. April 3, 2014. Overview. Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws Dependent Sources. 5 Ideal Basic Circuit Elements. Voltage Sources Current Sources
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Lecture 2:Circuit Elements & SchematicsNilsson 2.1-2.5 ENG17 (Sec. 2): Circuits I Spring 2014 April 3, 2014
Overview • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources
5 Ideal Basic Circuit Elements • Voltage Sources • Current Sources • Resistors • Inductors • Capacitors
Ideal Sources Voltage Source (const. voltage) Current Source (const. current)
Dependent Sources Voltage Sources Current Sources
Schematics - GND • Ground (GND) is a common connection • Typically connect to Earth GND • Always a zero [V] reference potential
Overview • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources
Conductance • Conductance, G • Units: siemens [S]
Power & Ohm’s Law Ohm’s Law Power Relationship Therefore…
Overview • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources
Additional Elements Short Circuit Open Circuit Switch
Schematic 1.5V 9V
Overview • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources
Kirchhoff’s Current Law (KCL) 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) 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
Overview • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources
Finding vo KVL: KCL: Ohm’s Law:
Recap • Voltage & Current Sources • Electrical Resistance • Circuit Model • Kirchhoff’s Laws • Dependent Sources