BASIC ELECTRICITY
MAGNETISM
Jaime Licuanan,ECE,CCNA
ELECTRICITY
• A phenomenon that is associated with the
presence and motion of electrons and other
charged particles
Jaime Licuanan,ECE,CCNA
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NUCLEUS
+
++
K
L
M
Jaime Licuanan,ECE,CCNA
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BASIC ELECTRICAL QUANTITIES
CHARGE (Q)
Laws of Electric Charges
• Unlike or dissimilar charges attract each other
• Like or similar charges repel each other
Coulomb’s Law
• “The force of repulsion or attraction between charges is
proportional to the amount of charges and inversely
proportional to the square of the distance between
charges”
kQ1Q2
F = r2
Jaime Licuanan,ECE,CCNA
Current
- Charge per unit time
- Direction of electron flow
Electromotive force
How Voltage is Produced?
1. Friction
2. Pressure
3. Heat
4. Light
5. Chemical action
6. Magnetism
Jaime Licuanan,ECE,CCNA
Resistance
-opposition to current flow in ohms
-electrical property
-determine by physical factors
Factors affecting resistance of wire
1. Type of material
2. Dimensions (area and length)
L
R=
A
3. Frequency
4. Temperature
Materials whose resistance is affected by temperature
a. Positive temperature coefficient
b. Negative temperature coefficient
c. Zero temperature coefficient
Jaime Licuanan,ECE,CCNA
Review Problem:
1. A copper wire initially has a length of 6 cm with
a radius of 10 mm at 2 degrees C, what will be
its final resistance when it is being heated
across a fire 100 degrees C in temp?
Jaime Licuanan,ECE,CCNA
ELECTRONIC COMPONENTS
RESISTOR
-electrical device that oppose flow of current
-can be fixed or variable
-wattage determines the size
Jaime Licuanan,ECE,CCNA
COLOR
BAND1
Black
0
Brown 1
Red
2
Orange 3
Yellow 4
Green 5
Blue
6
Violet
7
Gray
8
White
9
Gold
-Silver -JaimeNo
Licuanan,ECE,CCNA
Color--
BAND2
0
1
2
3
4
5
6
7
8
9
----
Multiplier
10^0
10^1
10^2
10^3
10^4
10^5
10^6
10^7
10^8
10^9
0.1
0.01
Tolerance
-1%
2%
3%
4%
-----5%
10%
20%
Jaime Licuanan,ECE,CCNA
INDUCTOR vs CAPACITOR
Jaime Licuanan,ECE,CCNA
INDUCTOR
CAPACITOR
-opposes change in current
-stores energy through
electromagnetic field
-opposes change in voltage
-stores energy through
electrostatic field
a. Inductance
a. Capacitance
2
L =  0  r AN
L
b. Time constant
λ= L
C=
b. Time constant
λ=
R
c. Instantaneous Current of an
inductor
I(t) = E (1-e^(- (t/λ) )
R
Jaime Licuanan,ECE,CCNA
c. Instantaneous Voltage of a
capacitor
V(t) =
d. Voltage across an inductor
d. Current across a capacitor
V = L( di/dt)
= N ( d)
I=
dt
e. Energy stored
W = 1/2LI^2
f. Inductive reactance
XL = 2πfL
Jaime Licuanan,ECE,CCNA
e. Energy stored
W=
f. Capacitive reactance
Xc=
Review Problems
3. A 12 V DC source is suddenly applied to an inductive
coil whose resistance and inductance are 10 ohms and
20 mH respectively. Approximately how long will it take
before the current through the coil settles to its final
value?
4. An RL circuit has R =2 ohms and L = 4 H. The time
needed for the inductor current to reach 40 % of its
steady state value is________.
5. A 6-H coil whose resistance is 24 ohms is connected in
series with a 24-ohm resistor to a 144 V battery and a
switch. The switch is closed at t = 0. Determine the
energy stored in the magnetic field.
Jaime Licuanan,ECE,CCNA
6. The total capacitance of two 40 mF series connected
capacitors in parallel with a 4 mF capacitor is?
7. A capacitor with a working voltage of 300 V would
normally have an effective voltage of ________.
(see what happens with overvoltage capacitor)
Jaime Licuanan,ECE,CCNA
BREAK
Jaime Licuanan,ECE,CCNA
MAGNETISM
-a natural phenomenon where some material
attract some other material
MAGNETIC THEORIES
1. Weber’s Theory
-postulates that all magnetic material has tiny molecular
magnets
2. Domain Theory
- Unbalanced spins of electrons create magnetism
Jaime Licuanan,ECE,CCNA
Magnetic Quantities
1. Flux
-magnetic lines of force
-in electric circuit, it is the current
- Maxwells, Weber
2. Flux Density
- Flux per unit area
- Gauss, Tesla
3. Magnemotive Force (mmf)
- Coercive force
Jaime-Licuanan,ECE,CCNA
Gilberts, ampere-turn
4. Magnetic Field Intensity
-magnemotive force per unit length
MATERIALS ACCORDING to Permeability
a. Ferromagnetic
b. Paramagnetic
c. Non magnetic
d. Diamagnetic
Jaime Licuanan,ECE,CCNA
MAGNETIC PROPERTIES
HYSTERESIS
• the delayed reaction of the magnetization of a ferromagnetic
material with the change of the magnetizing force
Jaime Licuanan,ECE,CCNA
Jaime Licuanan,ECE,CCNA