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Circuit Analysis

- Basic Concepts -

Circuit Analysis

 DEVELOP TOOLS FOR THE

ANALYSIS AND DESIGN OF BASIC

ELECTRIC CIRCUITS

Potential↔Flow Circuit

• A “Circuit” describes the Relationship

between

• Indestructible-Entity

(Mass, Heat, Charge)

Movement or FLOW

• Energy-Producing

POTENTIAL (Gravity,

Pressure, Voltage,

Temperature)

Electro-Fluidic Analogy

• Analogous Fluidic and Electrical Circuits
• Examine Individual Circuit Elements

Fluidic Electrical

Flow (Mass Movement) Source

• Current is the Electrical MASS-FLOW

Incompressible-Fluid Flow-

Source → Positive

Displacement Pump (NO fluid

slip)

Electrical Current Source →

Current Source

Conductors (move mass)

• Perfect Conductors transport “Flow” with NO

LOSS of Potential

Flow On/Off Control

• Valves & Switches Turn Flow On/Off

Flow On/Off → ShutOff Valve;

typically “Ball”, “Plug” or “Gate”

type

Electrical

Current On/Off → 2-Pole,

Single-Throw (2PST) Switch

Capacitor  Accumulates Flow

• Capacitors Produce a Flow-Change when

Pressure Changes

A Balloon would be a form of Fluidic Capacitance. The Units for the Fluidic Capacitance, Cf , are inverse m∙s 2

The Units of Electrical Capacitance are A∙s/V

Another Circuit Analogy

• Resistors in “Series
  • Note that “Flow” moves from HI-potential to

LO-potential in BOTH Cases

Electric Circuit – What is it?

• ELECTRIC CIRCUIT IS AN INTERCONNECTION

OF ELECTRICAL COMPONENTS

L

C

R 1

R 2

v (^) S −

v O

TYPICAL LINEAR CIRCUIT

a b

2 TERMINAL COMPONENT

characterized by the current through it and the voltage difference between terminals

NODE

NODE

International System of Units (SI)

• SI base units
  • The SI system of Units Is Founded On Units For

Seven Base Quantities Assumed To Be Mutually

Independent, As Given BelowSI Base Units

Base quantity Name Symbol length meter m mass kilogram kg time second s electric current ampere A thermodynamic temperature kelvin^ K amount of substance mole mol luminous intensity candela cd

http://physics.nist.gov/cuu/index.html

Only One “Electrical” Unit

SI DERIVED ELECTRICAL UNITS

• Other quantities, called derived quantities, are defined in terms of the seven base quantities via a system of quantity equations. The SI units for these derived quantities are obtained from these equations and the 7 SI base units

Derived quantity Name Symbol

Expression in terms of other SI units

Expression in terms of SI base units

Frequency hertz Hz - s -

energy, work, quantity of heat joule J N·m m 2 ·kg·s-

power, radiant flux watt W J/s m 2 ·kg·s-

electric charge, quantity of electricity coulomb C - s·A

electric potential difference, electromotive force volt^ V^ W/A^ m^

(^2) ·kg·s-3·A -

capacitance farad F C/V m -2·kg-1·s^4 ·A 2

electric resistance ohm Ω V/A m 2 ·kg·s-3·A -

electric conductance siemens S A/V m -2·kg-1·s^3 ·A 2

inductance henry H Wb/A m 2 ·kg·s-2·A -

Derived Units

• One Ampere Of Current Carries One

Coulomb Of Charge Every Second

A = C s

C

J V =

• 1 Coulomb = 6.242x 18 e -
• e-^ ≡ The Charge On An Electron

 A Volt Is A Measure Of Energy

Per Charge ( Electrical Potential )

• Two Points Have A Potential Difference Of

One Volt If One Coulomb Of Charge Gains

One Joule Of Energy When It Is Moved

From One Point To The Other.

Derived Units cont.

• The Ohm Is A Measure Of The Resistance

To The Flow Of Charge

• There Is One Ohm Of Resistance If It Requires

One Volt Of Electrical-Pressure To Drive

Through One Ampere Of Current

A

V Ω =

W = V × A

 One Watt Of Power Is Required To

Drive One Ampere Of Current Against

An Electromotive Potential Difference

Of One Volt