CIRCUIT ANALYSIS ENGR. VIKRAM KUMAR B.E (ELECTRONICS) M.E (ELECTRONICS SYSTEM ENGG:) MUET JAMSHORO 1 OHM’S LAW

AMPS volts Ammeters measure current in amperes and are always wired in series in the circuit. Voltmeters measure potential in volts and are always wired in parallel in the circuit. 2

wiring battery voltmeter ammeter resistance capacitor + - A V junction terminal AC generator Variable resistance Variable capacitor 3

ELECTRON PUMP (SOURCE VOLTAGE) [ENERGY IN] LOAD (RESISTANCE) [ENERGY OUT] CONDUCTOR ELECTRONS OUT OF SOURCE ELECTRONS OUT OF LOAD ELECTRONS BACK TO SOURCE ELECTRONS INTO LOAD HIGHER ENERGY ELECTRONS LOWER ENERGY ELECTRONS CONDUCTOR 4

Potential In volts (joules / coul) Current In amperes (coul / second) Resistance In ohms (volts / amp) Drop across a resistance Current passing Through the resistor 5

volts Battery current Electrons have Less Energy Electrons have More Energy Electrons get An energy boost current 6

volts Resistor current Electrons have More Energy Electrons have Less Energy Energy is lost In the resistor 7

4.2 - Ohm’s Law  Every conversion of energy from one form to another can be related to this equation.  In electric circuits the effect we are trying to establish is the flow of charge, or current. The potential difference, or voltage between two points is the cause (“pressure”), and resistance is the opposition encountered.

Ohm’s Law  Simple analogy: Water in a hose  Electrons in a copper wire are analogous to water in a hose.  Consider the pressure valve as the applied voltage and the size of the hose as the source of resistance.  The absence of pressure in the hose, or voltage across the wire will result in a system without motion or reaction.  A small diameter hose will limit the rate at which water will flow, just as a small diameter copper wire limits the flow of electrons. 9

Ohm’s Law Where:I = current (amperes, A) E = voltage (volts, V) R = resistance (ohms,  )

4.3 - Plotting Ohm’s Law 11

There are three generally types of electrical circuits: (1)Series circuits in which the current created by the voltage source passes through each circuit component in succession. R2R2 A2A2 R1R1 R3R3 A1A1 Arrows show Current path Through each component 12

(2) Parallel circuits in which the current created by the voltage source branches with some passing through one component and while the rest of the current passes through other components. Arrows show Current path Through each component Junction or Branching points A1A1 R1R1 R2R2 R3R3 A2A2 A3A3 A4A4 R4R4 13

(3) Series Parallel circuits or combination circuits which contain series segments and parallel segments. R1R1 R2R2 R3R3 A1A1 A2A2 A3A3 A4A4 R4R4 SERIES PARALLELPARALLEL Arrows show Current path Through each component 14

All electrical circuit analysis requires the use of two fundamental laws called Kirchhoff’s Laws 15

FIRST LAW All current entering a junction point must equal all current leaving that junction point Junction point Current Entering ( I 1 ) Current Leaving ( I 2 ) Current Leaving ( I 3 ) I 1 = I 2 + I 3 16

SECOND LAW Around any complete loop, the sum of the voltage rises must equal the sum of voltage drops Battery (voltage rise) Resistance 1 (voltage drop 1) Resistance 2 (voltage drop 2) Resistance 3 (voltage drop 3) Current flow Complete loop V (Battery) = V 1 + V 2 + V

R2R2 R1R1 A2A2 A1A1 AtAt V1V1 EMF Kirchhoff’s Laws Around a loop  V rises =  V drops A loop is a completed Path for current flow Battery V2V2 Loop #1 Loop #2 Loop #3 + - Complete current Paths in a circuit 18

When using Kirchhoff’s laws we apply the principles of conventional current flow. When current leaves the positive (+) terminal of a voltage source and enters the negative (-) terminal a voltage rise occurs across the source. If the current enters the positive and exits the negative a of a voltage source a voltage drop occurs across the source. When tracing a current loop, if the assumed direction of the current and the loop direction are the same, a voltage drop occurs across a resistance. If the assumed direction of the current and the loop direction are opposite, a voltage rise occurs across the the resistance. 19

Battery ( 6 volts) + - Current flow V = + 6 v Current flow V = - 6 v When using Kirchhoff’s laws we apply the principles of conventional current flow. When current leaves the positive (+) terminal of a voltage source and enters the negative (-) terminal a voltage rise occurs across the source. If the current enters the positive and exits the negative a of a voltage source a voltage drop occurs across the source. 20

When tracing a current loop, if the assumed direction of the current and the loop direction are the same, a voltage drop occurs across a resistance. resistor V = + 6 v A voltage rise Assumed Current flow V = - 6 v A voltage drop Loop direction Assumed Current flow Loop direction If the assumed direction of the current and the loop direction are opposite, a voltage rise occurs across the the resistance. 21

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