Chap1 Circuitos Analysis , Formulas and forms for Circuit Theory. University of Puerto Rico (PR)

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Slide 1

INEL 3105 – Electrical Systems Analysis I 2/19/2018

Basic Concepts 1

Objetivos del Curso Desarrollar el conocimiento, las destrezas y las técnicas fundamentales para el análisis DC y AC de circuitos eléctricos sencillos. Estudiar y analizar circuitos con elementos básicos, tales como transformadores, amplificadores operacionales, resistores, inductores y capacitores, utilizando las leyes de Kirchhoff y los teoremas de simplificación eléctrica de Thevenin y Norton.

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Basic Concepts → Chapter #1

System of Units Basic Electrical Quantities Independent & Dependent Sources Circuit Analysis

Basic Concepts

Systeme International des Unites – SI: Meter (m) Kilogram (Kg) Second (s) Ampere (A) Kelvin (K) Candela (cd)

SI - Standard Prefixes

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Basic Electrical Quantities → Current

Electric Current – rate of change of charge

Basic Concepts

Typical Current Magnitudes

�� �� = ����(��)

���� [A = C/s]

Conventional current flow +I represents movement of positive charges

Direct Current (DC)Alternating Current (AC)

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Basic Electrical Quantities → Energy

Energy – ability to do work

Basic Concepts

Flashlight Circuit

w �� [J = N∙m]

Convention: Absorbing Energy: positive current

enters the positive terminal

Supplying Energy: positive current enters the negative terminal

Energy AbsorbedEnergy Supplied

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Basic Electrical Quantities → Voltage

Voltage (potential) - energy required to move a unit positive charge

between to points with an energy level differential

difference in energy level of a unit charge located at each of the two points

Basic Concepts

Typical Voltage Magnitudes

���� �� = ����

���� = ���� �� − ���� �� [V = J/C]

The + and - signs define a reference direction

Voltage Representations

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Basic Electrical Quantities → Power

Power (potential) – rate of change of energy

Basic Concepts

�� = ����

���� = �� ∙ �� [W = J/s]

passive sign convention: the variable for the voltage v(t) is defined as the voltage across the element with the positive reference at the same terminal that the current variable i(t) is entering

Power positive – power being absorbed Power negative – power being supplied

Tellegen’s Theorem: the sum of the powers absorbed by all elements in an electrical network is zero!

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Example 1.3

Basic Concepts

Determine the unknown voltage or current.

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Independent Sources

A two-terminal element that maintains a specified voltage/current between it terminals regardless of the current through it.

Basic Concepts

Voltage Source Current Source

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Problem 1.13

Basic Concepts

The power absorbed by the BOX in Fig. P1.13 is: �� ∙ ��−����W Calculate the amount of charge that enters the BOX between 0.1 and 0.4 seconds.

INEL 3105 – Electrical Systems Analysis I 2/19/2018

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Example 1.7

Basic Concepts

Use Tellegen’s theorem to find the current I0 in the network provided.