Download Basic Current and Voltage Principles

Basic Current and Voltage Principles
Online Resource for ETCH 213
Faculty: B. Allen
Electron – Smallest subatomic particle of negative charge that
orbits the nucleus of an atom.
Voltage (V or E)
Current (I)
Resistance (R)
Power – Measured in watts or joules/second
Element – 107 different elements
Atom – Smallest particle of an element
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Exponents
Base number raised to an exponent
24
2 raised to the 4th power
2×2 × 2 × 2 = 24 = 16
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Roots of a number
The root of a number is a fractional exponent
5
4
10
5
=
=
1
2
10
1
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4
Powers of 10
4100 = 41 × 10 2
54000 = 54 × 103
0.000000834 = 834 × 10-9
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Scientific notation
The decimal point is placed after the first non-zero digit
4100 = 4.1 × 10 3
54000 = 5.4 × 104
0.000000834 = 8.34 × 10-7
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Engineering notation
A number greater than 1 times a power of 10 that is some
multiple of 3.
4100 = 4.1 × 10 3
54000 = 54 × 103
0.000000834 = 834 × 10-9
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Metric prefixes
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Using metric prefixes
4100 = 4.1k
54000 = 54k
0.000000834 = 834n
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Atom
Subatomic particles
-Electrons
-Protons
-Neutrons
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Atomic number
The number of protons in the nucleus of an
atom is the atomic number.
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Shells or bands
The shells or bands of an atom are the orbital
path containing a group of electrons that have a
common energy level.
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Valance shell or ring
The outermost shell formed by electrons in an
atom is called the valence shell or ring.
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Charges are positive, negative,
or neutral
Protons have a positive charge.
Electrons have a negative charge.
Neutrons have a neutral charge.
Like charges repel.
Unlike charges attract.
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Current
The movement of electrons
from one point to another
or
valence electrons moving
from one point to another.
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Coulomb of charge
1 coulomb (Q) of charge is 6.24 × 1018 electrons.
Q=
Total number of electrons
18 electrons
6.24 ×10
coulomb
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Ampere
Ampere is the unit of current.
1 ampere
=
1 coulomb
1 sec ond
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Conventional current versus
electron current flow
Conventional Current Flow – A current
produced by the movement of positive charges
towards a negative terminal.
Electron Current Flow – A current produced
by the movement of free electrons towards a
positive terminal.
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Measuring current with an
ammeter
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Voltage
Voltage is a force or pressure exerted on electrons
Electromotive Force (EMF) – A force that causes the
motion of electrons due to a potential difference
between two points.
Potential Difference– Voltage difference between
two points which will cause current to flow in a
closed circuit. Online Resource for ETCH 213
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Symbols
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Unit of voltage - Volts
3000 V = 1kV = 1 kilovolts
0.018V = 18mV = 18 millivolts
1,500,000V = 1.5MV = 1.5 megavolts
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Measure voltage across a
component of a circuit
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Current is proportional to
voltage
As I
V
As I
V
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Conductors allow current to flow and have
low resistance (R).
Conductance (G) = 1/Resistance (R)
Insulators have high resistance and prevent
current flow.
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Open circuit– no path for current
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Closed circuit – path for current
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Short circuit – large currents to
ground
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This ends
Basic Current and Voltage Principles
Online Resource for ETCH 213
Faculty: B. Allen