Fundamentals of Electric Circuits1: June 2014

"Power"

The electric power in watts associated with a complete electric circuit or a circuit component represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, e.g., heat, mechanical energy, or energy stored in electric fields or magnetic fields. For a resistor in a D C Circuit the power is given by the product of applied voltage and the electric current:

P = VI Power = Voltage x Current

Types of Elements:

Active Elements - Capable of generating energy. Examples are batteries & generators. – Negative Power
Passive Elements - Absorbs energy. Examples are capacitors &
inductors. – Positive Power

"CHAPTER 2" - Basic Laws
Ohm's Law:

Ohm's law states that the voltage (v) across a resistor is directly proportional to the current (i) flowing through the resistor (r).

"Ohm's Law Triangle"

To apply Ohm’s law as stated, we must pay careful attention to the current direction and voltage polarity. The direction of current (i) and the polarity of voltage (v) must conform with the passive sign convention. This implies that current ﬂows from a higher potential to a lower potential in order for v = iR. If current ﬂows from a lower potential to a higher potential, v = − iR.

Short Circuit:

Since the value of R can range from zero to inﬁnity, it is important that we consider the two extreme possible values of R. An element with R = 0 is called a short circuit.
For a short circuit,

v = iR = 0

Showing that the voltage is zero but the current could be anything. In practice, a short circuit is usually a connecting wire assumed to be a perfect conductor. Thus,

A short circuit is a circuit element with resistance approaching zero.

Open Circuit:

Similarly, an element with R = ∞ is known as an open circuit. For an open circuit,

indicating that the current is zero though the voltage could be anything. Thus,

An open circuit is a circuit element with resistance approaching inﬁnity.

Conductance:

A useful quantity in circuit analysis is the reciprocal of resistance R, known as conductance and denoted by G:

The conductance is a measure of how well an element will conduct electric current. The unit of conductance is the mho (ohm spelled backward) or reciprocal ohm. Although

engineers often use the mhos, in this book we prefer to use the siemens (S), the SI unit of conductance:

Thus,

Conductance is the ability of an element to conduct electric current; it is measured in mhos or siemens (S).

Some Learnings:

We will know if element is active or passive by the sign convention. When the current enters the (-) negative terminal & leaves the (+) positive terminal, the current is negative & the power is negative. Thus, the element is active. Otherwise, it is passive.

In Ohm's Law, it can be illustrated as follows:

When a person pushes a table, the table moves when the force given is enough for it to move. In relation to the ohm's law, the voltage is the force given, the current is the motion, and the resistance is the frictional force.

Laboratory:

We are given a basic a basic laboratory equipment & components. Some of that are:

Transistor

Integrated Circuit

Inductor

Variable AC

Variable DC

Digital Multimeter

Videos:

For more information you can watch the video below.

For Electric Power:

For Ohm's Law:

Again, Thank You so much
for visiting my blog.
GOD Bless !!!

By:

AYALA, ARNY S. BSECE -3

ECE 311

Professor:

ENGR. JAY S. VILLAN, MEP

"CHAPTER 1" - Basic Concepts

This is my first electrical subject for my Electronics Engineering course. It is so exciting and challenging. I really need not to forget my past subjects especially the Mathematics & Science subjects because I am going to apply all my knowledge for my solutions to the exercises/problems.

Our first topic was about the Basic Concepts. So obviously we discussed of “What is Electric Circuit?" and the definitions of some basic concepts. Some of the basic concepts are charge q(t), current i(t), voltage v(t), power p(t), energy w(t), & circuit elements.

Definitions:

Electric Circuits - An electric circuit is a path in which electrons from a voltage or current source flow. Electric current flows in a closed path called an electric circuit. Electrical elements that are connected together.

Charge q(t) - There are two types of electric charges, positive and negative. Positively charged substances are repelled from other positively charged substances, but attracted to negatively charged substances; negatively charged substances are repelled from negative and attracted to positive. - Measured in
coulombs (C).

Current i(t) - An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. - Measured in amperes (A).

Voltage v(t) - Is the electric potential difference between two points, or the difference in electric potential energy of a unit charge transported between two points. - Measured in volts (V).

Power p(t) - Electric power is the rate at which electric energy is transferred by an electric circuit. Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries. - Measured in watts (W).

Energy w(t) - Is energy newly derived from electrical potential energy. When loosely used to describe energy absorbed or delivered by an electrical circuits "electrical energy" refers to energy which has been converted from electrical potential energy. - Measured in joules (J).

Formulas: (Technique - Ohms Law Formula Wheel)

Some Learnings:

I also learned that we have to wear slippers always at home to prevent electrical shock / to prevent us from being electrocuted.
Clean sockets to avoid some accidents like electrocution.