2. RESISTIVE CIRCUITS CIRCUITS by Ulaby & Maharbiz Piezoresistive sensor All rights reserved. Do not reproduce or distribute. ©2013 Technology and Science Press

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Ohm’s Law Voltage across resistor is proportional to current Resistance: ability to resist flow of electric current  resistivity All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Conductivity All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Resistor Codes All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example 2-1: dc Motor = 98% of P What fraction of power supplied by the battery is dissipated in the motor? Solution: All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Tech Brief 2: Superconductivity  Critical temperature T C is the temperature at which a material becomes superconducting (zero resistance & no power dissipation) All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Kirchhoff’s Current Law Sum of currents entering a node is zero Also holds for closed boundary All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Kirchhoff’s Voltage Law (KVL) Sum of voltages around a closed path is zero Sum of voltage drops = sum of voltage rises All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example : KCL/KVL Determine all currents & voltages Solution: Three equations w/three unknowns: Loop 1 Loop 2 All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

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Equivalent Circuits  If the current and voltage characteristics at nodes are identical, the circuits are considered “equivalent”  Identifying equivalent circuits simplifies analysis All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Resistors in Series Equivalent resistance (series) is sum of resistances Voltage divided over resistors (voltage divider) All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Adding Sources In Series Unrealizable Circuit Combining voltage sources All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Resistors in Parallel All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Source Transformation Hence, For the two circuits to be equivalent : All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example 2-10: Source Transformation All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Circuit with no two resistors sharing the same current or same voltage R1,R2,R3=Delta R3,R4,R5=Delta R2,R3,R5=Y R1,R3,R4=Y All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

( Assuming no connection at node 3) Hence, All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Simultaneous solution leads to: All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example 2-12: Y- Δ Circuit All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

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Wheatstone Bridge  Measurement instrument based on differential measurement  Balanced Condition:  Determine unknown resistance based on “balanced” condition For balanced condition All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Wheatstone Sensor Determine Vout All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Tech Brief 3: Resistors As Sensors  Piezoresistive Sensors All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Tech Brief 3: Resistors As Sensors  All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Tech Brief 3: Resistors As Sensors Thermistor Sensors All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Example 2-16: Piezoresistor Cantilever (400 times greater than w/o cantilever) All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Linear i-v relationships All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

The Diode Current can flow only from + to – through a diode. All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

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Multisim  SPICE simulator software  Powerful tool for analyzing circuits  See tutorial and examples on CD that accompanies the text All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Multisim: Creating a Circuit All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Multisim: DC Operating Point Solution All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Multisim Solution Window All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Summary All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press