2. Atomic Structure
Atoms are the smallest particles of the element
composed of
-protons – positively charged particles
-neutrons – neutral particles
-electrons – negatively charged particles
Protons and neutrons are located in the nucleus.
Electrons are found in orbit surrounding the
nucleus.
1898 Joseph John Thompson
6. Atomic StructureAtomic Structure
Each proton and neutron has a mass of
approximately 1 dalton.
The sum of protons and neutrons is the atom’s
atomic mass.
Isotopes – atoms of the same element that
have different atomic mass numbers due to
different numbers of neutrons.
7. ATOMIC STRUCTUREATOMIC STRUCTURE
the number of protons in an atom
the number of protons and
neutrons in an atom
HeHe
22
44Atomic mass
Atomic number
number of electrons = number of protons
11. An ion is formed when an atom, or group of atoms, has a
net positive or negative charge (why?).
If a neutral atom looses one or more electrons
it becomes a cation.
If a neutral atom gains one or more electrons
it becomes an anion.
Na
11 protons
11 electrons Na+ 11 protons
10 electrons
Cl
17 protons
17 electrons Cl-
17 protons
18 electrons
12. What is electronics?
• Electronics is the branch of physics and technology
concerned with the design of circuit using transistor & micro
chip with behavior and movement of electrons in a conductor
etc.
• Electricity is the flow of electrons in a conductor
• Four main quantities:
– Voltage (volts) (V)
– Current (amps) (I)
– Resistance (ohms) (R)
– Power (watts) (P)
• Equations
– V = I x R
– P = V x I
– P = I x I x R
13. Terms
• Voltage
– Unit of potential difference or electromotive force. One volt is the
potential difference needed to produce one ampere of current
through a resistance of one ohm.
• Current
– Rate of flow of electrons through a conductor
• Resistance
– Electrical resistance is a measure of the degree to which a body
opposes the passage of an electric current.
• Power
– Measure of energy over time (joules / second)
• AC / DC
– Alternating current versus direct current
14. Negative & Positive Charges
• What do the effects of electricity in TV, radio,
a battery, and lightening all have in common?
• Basic particles of electric charge with opposite
polarities.
15. Electrons-
• The smallest amount of electrical charge
having the quality called negative polarity.
• Electrons orbit the center of atoms.
16. Protons+
• The proton is a basic particle with positive
polarity.
• Protons are located in the nucleus of atoms
along with neutrons, particles which have
neutral polarity.
17. Parallel vs Serial circuits
• Serial - RT = R1 + R2
• Parallel -
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
18. What is a circuit?
• A flow of electricity
• A circuit needs to be complete for anything to
work
• Circuit diagrams – a way to show an overview
of circuits
22. Open circuit and short circuit
• Open circuit:
When any part of the path
is open or broken, the
circuit is open because
there is no continuity in
conducting path
• Shot circuit:
When the voltage source
has a closed path across
its terminals, but the
resistance is practically
zero. the result is too
much current flow
bypass the load
resistance.
23. Quiz:
What type of circuit is shown in each
of the following examples?
Open
circuit
Closed
circuit
29. Electrically, all materials fall into 1 of
3 classifications:
Conductors
Insulators
Semi-Conductors
Conductors
Have 1 valence electron
Materials in which electrons can move freely from atom to
atom are called conductors.
In general all metals are good conductors.
The purpose of conductors is to allow electrical current to
flow with minimum resistance.
30. Insulators
• Have 8 valence electrons
• Materials in which electrons tend to stay put and do not flow
easily from atom to atom are termed insulators.
• Insulators are used to prevent the flow of electricity.
• Insulating materials such as glass, rubber, or plastic are also
called dielectrics, meaning they can store charges.
• Dielectric materials are used in components like capacitors
which must store electric charges.
31. Semi-Conductors
• Have 4 valence electrons
• Materials which are neither conductors nor
insulators
• Common semi conductor materials are
carbon, germanium and silicone.
• Used in components like transistors
