Transcript Fundamentals of Electricity

Charges
Electrons
e-
P+
n
nucleus
Source of Electrons(Force)
Matter : Weight - Space
Solid
Liquid
Gas
Plasma
Atoms
valence
shell
eP
n
nucleus
Atoms
Atomic Number – Number of
Protons
Atomic Weight – Number of
Protons plus Neutrons
Number of Protons EQUALS
Electrons in a neutral atom
Ionization
The process where an atom gains
or loses an electron.
+
Na Cl
Na – Positive Ion
Cl – Negative Ion
Charges (q)
Like Charges (++
q-
q-
q+
q+
- -)
Charges (q)
Un-Like Charges (+ -)
q+
q-
Coulomb’s Law
Coulomb (C)
The quantity of
charge on an abject.
1C = 6.25 x 1018 e-
Coulomb’s Law
q-
Coulomb’s Law
q1
q2
What does the force
depend on?
Coulomb’s Law
q1
d
q2
1.The charge on q1 and
q2 .
2.The distance (d).
d
2
d
q-
Mathematical Model for
Coulomb’s Law Force (F)
q1
d
q2
F ∞ q1q2
F ∞ 1/d2
q1
d
q2
K q1q 2
F=
2
d
K = 9.0 X
9
10
2
2
N·m /C
q1
d=3cm
q2
-6
+6x10 C
q1= +6μC =
-6
q2= +3μC = +6x10 C
-2
d = 3cm = 3x10 m
K = 9.0 X
9
10
2
2
N·m /C
What is the force on q2?
K q1q2
F=
2
d
9X109N·m2/C2(6X10-6C)(6X10-6C)
2
-2
(3X10 m)
F=
q1
2
1.8X10 N
q2
Electric Fields
Think of gravity or
gravitational field to
understand electric
fields.
Electric Fields
vs
g
Gravity
Electric
++++++++++
Fields
neutral
neutral
----------
E
Electric
++++++++++
Fields
+
----------
E
+
Electric
++++++++++
Fields
----------
E
-
Electric Fields
A force field due to
electric charges.
A force on a charge due
to another chage.
E
Electric Field: Point Charge
r
q
kq
E = r2
Force on a charge ‘q’ in an
Electric Field
Q
q
F
E=q
F
E=q
E=
Newton
Coulomb
E=
N
C
Energy and Work
Energy and Work
+
-
It takes work to
move the “-” charge.
Electric Potential (Energy)
Voltage
+
q’
Work on q’
Joule
ΔV =
== volt
q’
Coulomb
Electric Potential (Energy)
Voltage
+
VA
q’
ΔV = VB - VA
VB
“Potential Difference”
Voltage
Electric Potential (Energy)
Voltage
Fd
ΔV =
q
F
E=
q
Eqd
ΔV = q
Electric Potential (Energy)
Voltage
ΔV = Ed
Example
Two parallel plates are given
opposite charges. A voltmeter
measures the electric potental
differnece to be 60V. The plates
are 3.ocm apart. What is the
magnitude of the electric field
between them.
----------
ΔV
d
E
++++++++++
ΔV=60.0V
D=0.030m
ΔV = Ed
ΔV
=E
d
60V
=E
0.03m
2000J/(m·C)= E
2000 N/C = E
Current
Flow of charge!
Charge - Coulomb(C)
6.24 X 1018 electrons
e e e eee e e e e ee e ee e
Leyden Jar
Conductors
Leyden Jar
+
+ +
+
+
+
-++-+
-+ +---+
---
Capacitor
A capacitor is a
passive electronic
component that
stores energy in the
form of an
electrostatic field.
Capacitor
Metal Plates
Insulating Material
Dielectric
Capacitor
+
e
e
-
e
e
e
ee
ee e e
e e e e eeee e
e
e
Capacitor
- - -- - - -++++ ++++
Zinc
-
Copper
Current
e e e eee e e e e ee e ee e
Number of electrons
passing a point in a
second.
Current
Symbol - I
Unit – Ampere (Amps)
Amperes - A
Force
e e e eee e e e e ee e ee e
Voltage
Potential Difference
Electromotive Force (EMF)
Voltage
Symbol - V
Unit – Volt
Volt - V
Resistance
Opposition to Current Flow
High Resistance
Insulator
Resistance
Opposition to Current Flow
Low Resistance
Conductor
Resistance
Opposition to Current Flow
High and Low Resistance
SemiConductor
Resistance
Symbol - R
Unit – Ohm
Ohm - Ω
Putting it all Together
Load
Source
Path
Homework: 1-1
Worksheet
Due: 9/9/02
Test: 9/9/02