The first in a series of lectures to introduce the concepts, principle, and practices of electrical engineering.

1. Introduction to
Electrical Engineering

2. Goal
To introduce the fundamental concepts
that govern the principles and
practices of electrical and
electronics engineering.

3. Electron
‣ Negatively charged particle, revolves
around nucleus of an atom.
Electrons are repelled by other electrons.
Absence of electron (hole) attracts electrons.
Like charges repel, opposites attracts.

4. Static vs. Current
ELectricity
‣ Static Electricity
‣ Charge does not flow.
‣ Current Electricity
‣ Charge flows along a conductor.
‣ Conventional Current Wisdom:
Flows from higher potential to
lower potential.
‣ Electron Flow Reality: Electrons
are repelled by negative charge
and attracted to positive charge.

5. Conductor vs. Insulator
‣ Conductor: Allows electrons
to flow.
‣ Copper Wire
‣ Insulator: Prevents
electrons from flowing.
‣ Rubber
‣ Semiconductors behave as
both.
‣ Silicon

6. The EE Basics
‣ Voltage (V)
‣ Electric “pressure” or
potential difference
between two points.
‣ Must exist for current to
flow.
‣ Volts - e.g. 2.5V
‣ Ground is nominally 0V,
serves as a reference
voltage.
‣ Current (I)
‣ Rate of electrons
flowing.
‣ Amperes or Amps - e.g. 5A

7. The EE Basics
‣ Resistance (R)
‣ Measure of how much a
material impedes
current flow.
‣ Ohms - e.g. 500KΩ
‣ Power (W)
‣ Measures the rate at
which energy is
consumed.
‣ Watts - e.g. 5mW

8. Direct vs. Alternating
Current
‣ Direct Current (VDC)
‣ Current flows in one
direction.
‣ Alternating Current (VAC)
‣ Current periodically
changes direction.
Frequency Amplitude Phase

9. Series vs. Parallel Circuits
Series
Current has only one path to
flow from source to ground.
Current around a series
circuit is the same, voltage
across each element varies
based on its resistance.
Parallel
Current has multiple paths to
return to ground.
Voltage across parallel
components is the same,
current through each
components varies based on
its resistance.

10. Calculating Resistor
Value for an LED
We want to add a Light Emitting Diode
to our circuit. What size resistor
do we add in series to the LED for it
to operate safely?

11. Find the “givens”:
Battery or Source Voltage
Vf or Forward Operating
Voltage of the LED.
Imax or maximum current
of the LED.
Both found in spec
sheets.
For our example assume:
Vbattery = 5V
Vf = 1.7V
Imax = 20mA

12. Vbattery = 5V
Vf = 0.7V
Imax = 20mA
Ohm’s Law
R = V / I
R = (Vbattery - Vf) / Imax
R = (5V - 1.7V) / .02A
R = 165 Ω
Reality is you will NOT find a 165 Ω. So
find the next LARGER value and use that.
For our solution, 180 Ω resistors are fairly
common.

13. Resistor value is HALF the
story.
We must also ensure the
proper POWER RATING.
If we do not allow for the
correct power dissipation,
component could catch fire!
Power = Voltage x Current
From last slide, resistor will have to
drop 3.3V and pass 20mA of current.
Power (Watts) = 3.3V x .02A
Power = 66mW

14. Again, you will not find a
resistor rated for 66mW.
Look for the next larger
value, typically 1/4W or
250mW is readily available.
So for our solution, we will need to
acquire a 180Ω resistor rated at 250mW.

15. Questions?