Introduction to Electrical Circuits

Electric Circuits

are an interconnection of electrical elements where a collection of components are connected via metal wires.

What year Electricity

1752

Electricity

Benjamin Franklin helped in the discovery of electricity using a kite, string, and iron key.

What year Steam Electricity

1776

Steam Electricity

Scottish inventor James Watt installed the first engines in commercial enterprises. In later years, his name was attributed to the unit of power.

What year Bioelectricity

1786

Bioelectricity

Luigi Galvani experimented that muscles of the frog in which in his discovery it has electric current. When a series of tissue muscles is soaked in brine, it produces the twitching movement.

What year Battery

1792

Battery

Alessandro Volta showed that when moisture comes in between two (2) different metals, it creates electric power. In later years, his name was attributed to the unit of electric potential difference.

What year Electrodynamics

1827

What year Ohm’s Law

1827

Electrodynamics

French mathematician André-Marie Ampère’s experiments and work led to the discovery of electrodynamics. In later years, his name was attributed to the unit of electric current.

Ohm’s Law

What year Direct Current (DC) Generators

1882

Direct Current (DC) Generators

Thomas Edison used his DC generator to provide electricity and illuminate the first New York street to be lit by electric lamps.

What year Alternating Current (AC) Generators

1885

Alternating Current (AC) Generators

George Westinghouse purchased and developed Nikola Tesla’s patented motor for generating AC.

Scientific Notation

It is a special way of expressing very large or very small numbers. It is scientifically used to represent accuracy and precision of data in decimal form.

International System of Units (SI)

international measurement language and a basis of standard of measurement that some countries follow for quantity and counting purposes.

Basic Unit

Derived Units

Notation Prefixes

First Quantity?

Length

Second Quantity?

Mass

Third Quantity?

Time

Fourth Quantity?

Charge

Fifth Quantity?

Temperature

Sixth Quantity?

Luminous Intensity

What is Basic Unit of “Length”?

Meter

What is Basic Unit of “Mass”?

Kilogram

What is Basic Unit of “Time”?

Second

What is Basic Unit of “Charge”?

Coulomb

What is Basic Unit of “Temperature”?

Kelvin

What is Basic Unit of “Luminours Intensity”?

Candela

What is Symbol of Meter

m

What is Symbol of Kilogram

kg

What is Symbol of Second

s

What is Symbol of Coulomb

C

What is Symbol of Kelvin

K

What is Symbol of Candela

Cd

What Equivalent

What Equivalent

S

What Equivalent

What Equivalent

Through Conversion

Throught Formulation

Elements of an Atom

Atom
Proton
Neutron
Electron

Atom

basic unit of matter; can be built up into elements

Proton

positively charged particle

Neutron

neutral charged particle

Electron

negatively charged particle

Charge

Relationship Between Charge and Current

Electric Current

(Electric Current):
1) What current must flow if 0.24 𝐶𝑜𝑢𝑙𝑜𝑚𝑏𝑠 is to be transferred in 15 𝑚𝑠?

(Electric Current):
2) If a current of 10 𝐴𝑚𝑝𝑠 flows for four (4) minutes, find the quantity of electricity transferred.

Voltage

(Electric Voltage):
1) Moving charge 𝑞 from point 𝑏 to point 𝑎 requires 25 𝐽. Find the voltage drop 𝑣𝑎𝑏 (the voltage at 𝑎 positive with respect to 𝑏) if (a) 𝑞 = 5 𝐶 and (b) 𝑞 = −10 𝐶.

(Electric Voltage):
2). An energy source forces a constant current of 2 𝐴 for 10 𝑠 to flow through a light bulb. If 2.3 𝑘𝐽 is given off in the form of light and heat energy, calculate the voltage drop across the bulb.

Energy

• It is the capacity to do work measured in joules (/).

• This confirms the fact that the total power supplied to the circuit must balance the total power

absorbed.

Power

Example (Energy and Power):
A mass of 1000 𝑘𝑔 is raised through a height of 10 𝑚 in 20 𝑠. What is a) the work done and b) the power developed? (Earth’s gravitational acceleration = 9.81 𝑚/𝑠².)

Energy Efficiency

Example (Energy and Power):
What would be the efficiency of a power amplifier if the input work is equal to 512 𝑘𝐽 and the output work is 230 𝑘𝐽?

Circuit Diagrams and Basic Symbols

In an electric circuit, there are different elements or components which make up a device or a system.

Circuit Diagram or Schematic

is a simplified graphical representation of components or elements in a system of circuits.

Two types of Switches

Open Circuit
Closed Circuit

Open circuit

switch opened

Closed circuit

switch closed

switch closed

Battery Symbols / Power Source

Battery Symbols of “Single cell”

Battery Symbols of “Multi cell”

Power Source of “DC battery source”

Power Source of “AC battery source”

Wirings Symbol of “No Contact / No Connection”

Wiring Symbol of “Connected / Full Contact”

Wiring Symbol of “Terminal”

Wiring Symbol of “Ground”

Resistors

Diodes

Transistors (Bipolar Junction Transistor or BJT)

The formula for the charge of an electron

𝑒 = −1. 𝟔𝟔𝟔𝟔𝟔𝟔 × 1𝟔𝟔−1𝟏𝟏 𝐶.

This formula is used to find the charge whenever current

𝑸 = 𝐼𝑡 (𝐶ℎ𝑎𝑟𝑔𝑒 = 𝐴𝑚𝑝𝑒𝑟𝑒 × t𝑖𝑚𝑒 𝑖𝑛 𝑆𝑒𝑐𝑜𝑛𝑑𝑠)

Formula of Voltage

Formula of Energy Efficiency

Formula of Power