Lecture-2 Electronic Components Electrical Engineering department Umm Al-Qura University Dr. Omar Abdulaziz Hafez

Lecture-2

Electronic Components

Electrical Engineering department Umm Al-Qura University Dr. Omar Abdulaziz Hafez

Resistors

— The main function of resistors in a circuit is to control the flow of current to other components.

— Take an LED (light) for example. If too much current flows through an LED it is destroyed. So a resistor is used to limit the current.

— Measured in Ohms W

— Have colored rings to indicate value

Resistors

— Power Rating

— Practical resistors are rated according to their maximum power dissipation.

— ¼ Watt, ½ Watt, 5 Watt

— If the average power dissipated by a resistor is more than its power rating what will happen?

— damage to the resistor may occur

— permanently altering its resistance

Slide 3

Parallel and Series

— More Resistance (Impedance) vs. More Conductance (Admittance)

3 2

1

1 1

1 1

R R

R

R_T = + +

3 2

1

R R

R

R

_T

= + +

W

= +

= +

+

= 11

2 6 10

10 1 10

1 6 1

RT

𝑅𝑇 = 𝑅1 𝑥 𝑅2 𝑅1 + 𝑅2

Activity

Slide 5

Capacitors

— Passive electronic component consisting of a pair of conductors separated by a dielectric (insulator).

— Temporary Charge Storage Device

— Measured in Farad (F)

time I

Capacitors Applications

— to block DC

— to filter noise

— to tune radio channels

— in memories

Slide 7

Parallel and Series

3 2

1

1 1

1 1

C C

C

C_T = + +

3 2

1

C C

C

C

_T

= + +

Inductors (Coils)

— Passive electrical component that can store energy in a magnetic field created by the electric current

passing through it

— Measured in Henry (H)

Slide 9

Inductors (Coils)

— Resists (reacts) AC current with delay

— block the flow of AC current while allowing DC to pass

— used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits, used to tune radio and TV receivers.

Parallel and Series

Slide 11

3 2

1

1 1

1 1

L L

L

L_T = + +

3 2

1

L L

L

L

_T

= + +

Basic Laws of Circuits

Ohm’s Law: ^{i(t) + v(t) _}

R

v(t) = Ri(t)

_ v(t) + i(t)

R

v(t) = ^_ Ri(t) The most important formula in electronics is Ohm's law:

Ohm’s law shows the relationship between the three main measurements used in a circuit: voltage, current, and

resistance. It also shows how the units that are used to

measure these relate to each other .1 volt will cause 1 amp of current to flow through 1 ohm; that same 1 V will cause 2 A through 0.5Ω

13

Two special resistor values

Circuit Short

Circuit Open -

= +

0

v i = 0

= 0

R R = ¥

Basic Laws of Circuits

Basic Laws of Circuits

Ohm’s Law:

Example 2.1.

+ _ 115V RMS

(ac) R

(100 Watt light bulb)

V

Determine the resistance of the 100 Watt bulb.

2

2 2

2 115

132.25 100

P VI V I R R

R V ohms

P

= = =

= = =

Voltage Drop

— A current passing through a load generates a voltage drop

Slide 15

R

i

v = ×

Question

— What is the total current drawn from the source?

R A I V

R

_L

5 2 10

5 3

2 3

4 //

4

=

=

=

W

= +

= +

=

Note:

to solve for single source:

1. Reduce the circuit to single loop circuit (series and parallel resistors)

2. Apply Ohm’s law

Electrical Engineering Umm Al-Qura University Slide 17

Question

Independent and Dependent

Sources

Independent and Dependent Sources

Slide 19

Fuses

— Protection devices

— Current limiting devices

— High current è wire melts è open circuit

Circuit Symbols

Circuit Breaker

— Re-usable fuse or switch

— Current increasesè Stronger Magnet è open circuit

— Reset breaker è current resumes

— Magnetic, Thermal, semiconductor breakers

Slide 21

Circuit Symbols

Relays

— A relay is an electromagnetic switch operated by a relatively small electric current that can turn on or off a much larger electric current. The heart of a relay is an electromagnet (a coil of wire that becomes a temporary

magnet when electricity flows through it)

— Current in a coil è Magnet è Pull a metal lever è change contact

— Can be used in turning lights or motors ON/OFF

Diodes

— Conducts current in one direction

— Many types with different applications

Slide 23

Transistors

— A semiconductor device used to amplify and switch electronic signals.

— At least three terminals for connection to an external circuit.

— A voltage or current applied to one pair of the transistor's

terminals changes the current flowing through another pair of terminals

Integrated Circuits

Slide 25

— Revolutionized the world of electronics.

— Used in almost all electronic equipment in use today

— Low cost of production of IC Computers, cellular phones, etc.

Intel 4004 Processor

(1971) 1000 Transistor 1MHz

i7 Processor

Other Components

— Each component does a specific function

— Each component has a symbol in circuits

— Each component has specifications

Slide 27