Introduction to
Basic Electronics
Lecture -2
Basic Electronics
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What is electricity?
Voltage, Current, Resistance
DC/AC
Ohm’s Law
Capacitors & Inductors
Conductor & Insulator
What is Electricity?
• Everything is made of atoms
• There are 118 elements, an atom is a single part of an
element
• Atom consists of electrons, protons, and neutrons
• Electrons (- charge) are attracted to protons (+ charge),
this holds the atom together
• Some materials have strong attraction and refuse to loss
electrons, these are called insulators (air, glass, rubber,
most plastics)
• Some materials have weak attractions and allow electrons
to be lost, these are called conductors (copper, silver,
gold, aluminum)
• Electrons can be made to move from one atom to
another, this is called a current of electricity.
• Surplus of electrons is called
a negative charge (-).
• A shortage of electrons is
called a positive charge (+).
• A battery provides a surplus
of electrons by chemical
reaction.
• By connecting a conductor
from the positive terminal to
negative terminal electrons
will flow.
Electricity
Electricity is the flow of electrons so it is
necessary to measure the charge.
The basic unit for measuring charge is the
coulomb or the letter C.
1 coulomb is equal to the charge of
6,250,000,000,000,000,000
electrons!!!
1C = 6.25 x 1018 electrons
Voltage
• A battery positive terminal (+) and a negative terminal (-). The
difference in charge between each terminal is the potential
energy the battery can provide. This is labeled in units of volts.
Water Analogy
Voltage Sources:
• Voltage is like differential pressure,
always measure between two points.
• Measure voltage between two points
or across a component in a circuit.
• When measuring DC voltage make
sure polarity of meter is correct,
positive (+) red, negative (-) black.
Ground
Current
Electric current is the amount of electrons, or charge,
moving past a point every second.
It is basically the speed of electron flow.
The faster the electron flow, the higher the current.
Current is represented by the letter I.
The basic unit for measuring current is ampere(A).
1 A = 1 coulomb/sec
= 6.25 x 1018 electrons /sec
Current
• Uniform flow of electrons thru a circuit is called current.
WILL USE CONVENTIONAL FLOW NOTATION
ON ALL SCHEMATICS
• To measure current, must break circuit and install meter in line.
• Measurement is imperfect because of voltage drop created by meter.
Current
Direct Current(DC)
The battery we have been using for a current/voltage
source generates direct current, which simply means the
current flows in only one direction.
Current
Alternating Current(AC)
The electrical current in your house is alternating current. This comes
from power plants that are operated by the electric company. Those big
wires you see stretching across the countryside are carrying AC current
from the power plants to the loads, which are in our homes and
businesses. The direction of current is switching back and forth 60 times
each second.
Resistance
 When an electron is knocked out of an atom, it will fly off and hit
another atom.
 If the electron strikes the atom with enough force, it will knock
off another electron.
 The atom that was just knocked off will hit another atom and so
forth.
 Note that every time an electron strikes another, it is transferring
its energy. Some of the energy is converted into heat every time
it is transferred.
 The voltage will drop as the energy is transferred over long distances.
Thus a long wire has a higher resistance than a short wire.
Resistance
• All materials have a resistance that is dependent on crosssectional area, material type and temperature.
• A resistor dissipates power in the form of heat
Various resistors types
When measuring resistance, remove
component from the circuit.
Resistor Color Code
Ohm’s Law
Prototyping Board
Example of how components are
Inserted in the protoboard
Conductor
 Copper is considered to be a conductor because it “conducts”
the electron current or flow of electrons fairly easily. Most metals
are considered to be good conductors of electrical current. Copper
is just one of the more popular materials that is used for
conductors.
 Other materials that are sometimes used as conductors are
silver, gold, and aluminum. Copper is still the most popular
material used for wires because it is a very good conductor of
electrical current and it is fairly inexpensive when compared to
gold and silver. Aluminum and most other metals do not conduct
electricity quite as good as copper.
Insulator
 Insulators are materials that have just the opposite effect on
the flow of electrons. They do not let electrons flow very easily from
one atom to another. Insulators are materials whose atoms have
tightly bound electrons. These electrons are not free to roam
around and be shared by neighboring atoms. Some common
insulator materials are glass, plastic, rubber, air, and wood.
 Insulators are used to protect us from the dangerous effects of
electricity flowing through conductors. Sometimes the voltage in an
electrical circuit can be quite high and dangerous. If the voltage is
high enough, electric current can be made to flow through even
materials that are generally not considered to be good conductors.
Insulator
 Our bodies will conduct electricity and you may have
experienced this when you received an electrical shock. Generally,
electricity flowing through the body is not pleasant and can cause
injuries. The function of our heart can be disrupted by a strong
electrical shock and the current can cause burns.
 Therefore, we need to shield our bodies from the conductors that
carry electricity. The rubbery coating on wires is an insulating
material that shields us from the conductor inside. Look at any
lamp cord and you will see the insulator. If you see the conductor, it
is probably time to replace the cord.
Capacitance
A capacitor is used to store charge for a short amount of time
Capacitor
Battery
Unit = Farad
Pico Farad - pF = 10-12F
Micro Farad - uF = 10-6F
Capacitor Charging
Capacitor Discharge
Inductance