This document provides an overview of key concepts in atomic structure and electronics. It discusses topics like voltage, current, resistance, capacitors, diodes, transistors, integrated circuits, logic gates, and printed circuit boards. Key points covered include definitions of voltage, current, resistance and their units of measurement. Circuit components like resistors, capacitors, diodes, transistors and how they function are also summarized.

2. Atomic Structure:

3. Voltage:
• Potential refers to the the possibility of
doing work.
• The symbol for potential difference is
E (for electromotive force)
• The practical unit of potential
difference is the volt (V)
• 1 volt is a measure of the amount of
work required to move 1C of charge

4. Current:
• When a charge is forced to move because of a potential
difference (voltage) current is produced.
• In conductors - free electrons can be forced to move with
relative ease, since they require little work to be moved.
• So current is charge in motion.
• The more electrons in motion the greater the current.
• Current indicates the intensity of the electricity in motion.
The symbol for current is I (for intensity) and is measured in
amperes.

5. Direction of Electron Flow
• The direction of electron flow in our circuit is from the negative side
of the battery, through the load resistance, back to the positive side
of the battery.
Direction of conventional current
• The direction of conventional current in our circuit is from the
positive side of the battery, through the load resistance, back to the
negativeside of the battery.

7. Direct Current:
• Circuits that are powered by battery sources are termed
direct current circuits.
• It is the flow of charges in just one direction
Alternating Current:
• An alternating voltage source periodically alternates or
reverses in polarity.
• The resulting current, therefore, periodically reverses in
direction.

9. Resistance:
• Opposition to the flow of current is termed
resistance.
• The fact that a wire can become hot from the flow
of current is evidence of resistance.
• Conductors have very little resistance.
• Insulators have large amounts of resistance.

10. Resistors
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Aresistor impedes the flow of electricity through a circuit.
Resistors have a set value.
Since voltage, current and resistance are related through Ohm’s
law, resistors are a good way to control voltage and current in
your circuit.

11. More onresistors
Resistor colorcodes
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1stband =
2nd band =
3rd band =
4th band =
1stnumber
2nd number
# of zeros / multiplier
tolerance

12. Colorcode
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13. Variableresistor/ Potentiometer
Apotentiometer is avariable resistor. As you manually
turn a dial, the resistance changes.
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14. Units
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Knowing your unitsis important!
Kilo and Mega are common in resistors
Milli, micro, nano and pico can be used in other
components
K(kilo) =1,000
M (mega) = 1,000,000
M (milli) = 1/1,000
u (micro) =1/1,000,000
n (nano) = 1/1,000,000,000 (one trillionth)
p (pico) = 1/ 1,000,000,000,000 (one quadrillionth)

15. Ohm’s Law:
• The amount of current in a circuit is dependent on its resistance and the
applied voltage. Specifically I = V/R
• If you know any two of the factors V, I, and R you can calculate the third.
•
Current I = V/R Voltage V = IR Resistance R = V/I

16. Capacitors
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Acapacitor stores electricalenergy.
Capacitance is measured in Farads. The small capacitors usually used in
electronics are often measured in microfarads and nanofarads.
Some capacitors are polarized. Note the
different length terminals on one of the capacitors.

17. 17
Capacitor working:

18. Diode
Adiode is a one way valve (or gate) for electricity. It is a
component with an asymmetrical transfer characteristic. A
diode has low (ideally zero) resistance in one direction, and
high (ideally infinite) resistance in the other direction.
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Diodes will protect your electronics.

19. P-N JUNCTION DIODE:

20. Diodecircuitprotection
In an electronic circuit, if the polarity is wrong, you can fry
your components.
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Diodes have abar
on the cathode
(negative) side.

21. Lightemitting diode(LED)
A light emitting diode (LED) is a semiconductor light source.
When electricity is passing through the diode, it emits light.
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22. Power Supply

23. TRANSFORMER

25. REctification

27. Transistors
Atransistor is a semiconductor device used to
amplify and switch electronic signals and electrical
power.
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This is our electronic switch!

28. Transistor water analogy:

29. Howatransistorworks
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Avoltage or current applied to one pair of the transistor’s
terminals changes the current through another pairof
terminals.
Atransistor is composed of semiconductor material with at
least three terminals
for connection to an external
circuit.
Transistors have 3pins.
For these transistors:
Collector
Emitter
Base

30. Terminology
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Useful asamplifiers.
BJTversus FET
Bipolar junction transistor.
Collector, Emitter, Base
Useful as motordrivers.
Field-effect transistor.
Source, Drain, Gate
MOSFET: Metal-oxide-semiconductor FET
NPN (N-channel FET) versus PNP (P-channel FET)
NPN versus PNP is how the semiconductors are layered.
NPN: Not pointing in
PNP: Pointing in permanently

31. Field Effect Transistor:

32. Schematicsymbols
BJTPNP BJTNPN
P-channel FET N-channel FET
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33. Integratedcircuit
An integrated circuit (IC) is a set of transistors that is
the controller or ‘brain’of an electronic circuit.
An input is received, an output is sent out.
Modern microprocessor ICs can have billions of
transistors per square inch!
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34. Logic Gates

35. Internal Structure of ICs.

36. Printed CircuitBoard
Components are attached to a printed
circuit board.
The ‘front’ side of the board will have
printed component information, such
as resistor # and resistance, diode type
and polarity,etc.
Holes go all the way through the board
from one side to the other. Through-
hole soldering is needed to connect
components to the board.
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37. Backof CircuitBoard
 The ‘back’ side of the board will have lines indicating
connections between components. The lines on the
back are similar to wires.
 Thicker lines denote more current (electrons) moving
through.
 Components connect the lines.
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