# EMLAB 1 Chapter 2. Resistive circuits 2014. 9. 12.

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EMLAB 1 Chapter 2. Resistive circuits 2014. 9. 12.

EMLAB 2 Contents 1.Ohm’s law 2.Kirchhoff’s laws 3.Series and parallel resistor combinations 4.Y-Δ transformation 5.Circuits with dependent sources

EMLAB 3 Entering resistive material, charges are decelerated, which decrease current flow. Resistors : microscopic view nucleus electrons

EMLAB 4 Types of resistors (1), (2), and (3) are high power resistors. (4) and (5) are high-wattage fixed resistors. (6) is a high precision resistor. (7)–(12) are fixed resistors with different power ratings.

EMLAB 5 1. Ohm’s law Power absorption : resistance ; conductance

EMLAB 6 Example 2.1 Determine the current and the power absorbed by the resistor.

EMLAB 7 Glossary (1) Node A node is simply a point of connection of two or more circuit elements. node Although one node can be spread out with perfect conductors, it is still only one node

EMLAB 8 (3) branch (2) loop A loop is simply any closed path through the circuit in which no node is encountered more than once a branch is a single or group of components such as resistors or a source which are connected between two nodes

EMLAB 9 2. Kirchhoff’s law (1) Kirchhoff ’s current law (KCL) : the algebraic sum of the currents entering(out-going) any node is zero → the sum of incoming currents is equal to the sum of outgoing currents. (2) Kirchhoff’s voltage law (KVL), the algebraic sum of the voltages around any loop is zero

EMLAB 10 Kirchhoff’s Current law R Current definition The direction of a current can be chosen arbitrarily. The value of a current can be obtained from a voltage drop along the direction of current divided by a resistance met. R2R2 R1R1 R3R3

EMLAB 11 Kirchhoff’s Voltage law Sum of voltage drops along a closed loop should be equal to zero! R1 C1 Voltage convention

EMLAB 12 Example 2.6 Find the unknown currents in the network. Node 1 : Node 2 : Node 3 : Node 4 : Node 5 :

EMLAB 13 Example E2.6 Find the current i x in the circuits in the figure.

EMLAB 14 Find V ad and V eb in the network in the figure. Example E2.8

EMLAB 15 Example 2.15 Given the following circuit, let us find I, V bd and the power absorbed by the 30kΩ resistor. Finally, let us use voltage division to find V bc.

EMLAB 16 Series resistors equivalent

EMLAB 17 Parallel resistors equivalent

EMLAB 18 Example 2.19 Given the circuit, we wish to find the current in the 12-kΩ load resistor. equivalent

EMLAB 19 Example 2.20 We wish to determine the resistance at terminals A-B in the network in the figure.

EMLAB 20 Y-Δ transformation equivalent Δ Y

EMLAB 21 Example 2.26 Given the network in Fig. 2.36a, let us find the source current I S.

EMLAB 22 2.8 Circuits with dependent sources Example 2.27 Let us determine the voltage V o in the circuit in the figure.

EMLAB 23 Example 2.28 Given the circuit in the figure containing a current-controlled current source, let us find the voltage V o.

EMLAB 24 Example 2.30 An equivalent circuit for a FET common-source amplifier or BJT common-emitter amplifier can be modeled by the circuit shown in the figure. We wish to determine an expression for the gain of the amplifier, which is the ratio of the output voltage to the input voltage. GND can be arbitrarily set.

EMLAB 25 Transistor Transistor amplifier

EMLAB 26 2.10 Application examples Example 2.33 : The Wheatstone bridge circuit.

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