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01JUNE 18 2011
Different type of Electric CircuitsCircuit Elements
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY1Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Electric Circuit An electric circuit consist of a voltage source, a load,a path for current between the source and the load.
A load is a device on which work is done by thecurrent through it.
Electric Circuit Types:1. Closed2. Open3. Short
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY2Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Voltage (V) It is the potential energy in an electrical circuit that makes things happen. It is sometimes called Electromotive Force or EMF. The basic unit (measurement) of EMF is volt.
Electric Potential. The amount of work required in moving a unit charge.Potential Difference. The rise and fall (gain or loss) of potential energy in
moving a charge from one point to another.Absolute Potential. Potential developed in moving a charge from infinity to a
point.Relative Potential. Potential developed in moving a charge from one point to
another point.
V = WQwhere W = energy in Joules (J)
Q = charge in Coulomb (C)
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY3Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Current (I) It is the flow of electrons in a conductor (wires) from the negative end to the positive end. It is measured in amperes (amps)
I = Qtwhere Q = charge in Coulomb (C)
t = time in sec (s)
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY4Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Resistance (R) It is the opposition to the flow of current. It is measured in ohms ().
R = lAwhere l = length in meter (m)
A = cross-sectional area in m2R = resistance in ohms () = resistivity or specific resistance
in ( m)= resistance per unit length andcross-sectional area
Notes:Resistivity for Annealed Cu at 20C
20C = 1.72 x 10-8 m (for annealed Cu)= 10.37 -cmil per ftCross sectional area in terms of square mils
1 cmil = sq. mils4
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY5Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Conductance (G) It is the ability for electricity to flow in a certain path It is measured in sigma ()
G = = A A l lwhere = conductivity or specific conductance in siemens per meter (S/m)
Notes:Annealed Cu posses 100% conductivityLess than 100% conductivity mean a poor conductorGreater than 100% conductivity means a better conductor
% conductivity = x 100% = x 100% material annealed Cu1/ material1/ Cu
% conductivity = x 100% Cu
material
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY6Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18, 2011
Thank You forlistening!
Lets discuss the Circuit Elements..
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY7Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
Different type of Electric CircuitsCircuit Elements
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY8Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
An electrical network is an interconnection of circuit element as follows:1. Voltage Source2. Resistors3. Inductors4. Capacitors5. Transmission Lines6. Switches
3. Inductor Inductor is a passive electrical component formed by a coil of wire thatexhibits the property of inductance.
Inductance is a measure of a coils ability to establish an induced voltageas a result of a change in its current, and that induced voltage is in adirection to oppose that change in current. Unit is Henry.
Is can store energy in a magnetic field created by the electriccurrent passing through it.
An Inductive load lags the applied voltage. Example of Inductive loads are hair dryers, fans, blenders, vacuumcleaners, and many other motorized devices.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY9Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
4. Capacitor Capacitor is a passive electrical component that stores electrical charge and aproperty of capacitance.
It is device made of two metal conductors separated by an insulator called dielectric. Capacitance is the amount of charge that a capacitor can store per unit voltage acrossits plate. Units is farads.
A Capacitive load leads the voltage. Example of capacitive loads are TV picture tubes, longextension cords, and components used in electronic devices.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY10Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY11Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
5. Transmission Line Transmission Line transfers bulkelectrical energy, from generatingpower plants to substationslocated near population centers.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY12Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
6. Switches Switches are commonly used for controllingthe opening or closing of a circuits,interrupting current or diverting it fromone conductor to another.
Type of Switch1. Mechanical Switches
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY13Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
SPST --- Single-Pole-Single-Throw DPST --- Double-Pole-Single-Throw DPDT --- Double-Pole-Double-Throw Push Button --- PB Rotary
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY14Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18 2011
2. Electrical Switches (Relay)It is an electromagnetic switch that is used to open or close electrical contactsrather than to provide mechanical movement.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY15Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 18, 2011
Thank You forlistening!
Lets discuss factors affecting Resistance of the Conductors..
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY16Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Resistance of the ConductorsFactors affecting the Resistance
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY17Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Resistance of the ConductorRecall R = lA
where l = length in meter (m)A = cross-sectional area in m2R = resistance in ohms () = resistivity or specific resistance
in ( m)= resistance per unit length andcross-sectional area
Notes:Resistivity for Annealed Cu at 20C
20C = 1.72 x 10-8 m (for annealed Cu)= 10.37 -cmil per ftCross sectional area in terms of square mils
1 cmil = sq. mils4
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY18Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Factors affecting the Resistance
1. Type of materials (conductor)2. Length of wire3. Cross-sectional area of wire4. Temperature
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY19Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY20Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY21Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
Thank You forlistening!
Lets discuss Temperature effect on the Resistance...
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Temperature Effect on the Resistance
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
Effect of Temperature on Resistance1. As temperature increases, Resistance increases (+ temp. coeff.)
eg. Cu, Al, and all metallic conductor2. As temperature increases, Resistance decreases (- temp. coeff.)
eg. Insulator and semiconductor3. As temperature increases or decreases, Resistance remains fairly constant
eg. Alloy, Mg
T
R
0TX
R1
t1
R2
t2
TX= inferred zero resistance temperature= inferred absolute zero temperature= - 234.5C (for Cu)
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
TR
0TX
R1
t1
R2
t2
By the law of Geometry,
=R2R1|Tx | + t2|Tx | + t1
R2 R1 |Tx | + t2|Tx | + t1=
Let s get R T curve as shownR2 - R1
R1t2 t1= |Tx | + t1
R2 - R1 R1 t2 t1= |Tx | + t1R2 = R1 t2 t1|Tx | + t1R1 +
R2 1 + (t2 t1)|Tx | + t1R1=1
But,
1 = 1|Tx | + t1= temp. coefficient of resistance at t1 per unit
resistance change per degree (C) change intemp. referred to a point on the R-T curve.
= RT1-R1 in per C
therefore,R2 = R1 1 + 1 (t2 t1)
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
Resistivity VS Temperature
T
0
1
t1
2
t2
Let m = slope of the linear region ofthe T curve
1t2 t12m = --
m (+2 = 1 t2- t1 )m12 1= 1 + (t2 - t1 )
but m1 = temp. coeff. of resistivity = 1
therefore,2 = 1 + t1 )1 (t2 -1
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
Thank You forlistening!
Lets discuss on the next Chapter: Ohms Law, Energy, Work, and Power...
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Electrical Relevance of Ohms Lawto DC CircuitWork, Electric Power andElectrical Energy
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Ohms LawStates that the current through a conductor between two points isdirectly proportional to the potential difference across the twopoints, and inversely proportional to the resistance between them.+
V
I
-
element
V Ibut there is always a constant figure that opposes tocurrent I, say this is kV = k x I=VI k
therefore, V = I x R
where R is the resistance for k whoopposes the current.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
Thank You forlistening!
Lets discuss Work, Electrical Energy, and Electric Power
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Electrical Relevance of Ohms Lawto DC CircuitWork, Electric Power andElectrical Energy
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
WorkWork is the accomplishment of motion againsta force that tends to oppose that motion.W = F x d
where, F = force in newtond = distance inmeterW = work in joules
Note: F = maweight = mg
Whenever Work is done, there is alwaysan accompanying energy conversion.
MMECHANICAL
ENERGY
GELECTRICALENERGY
HEAT ENERGY
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
Power Current itself does not do any real work. Voltage and Current together can produce real work. Electric Power is the product ofvoltage times current.
Power is used to producereal work.
Power is the rate of doingwork or energy conversion.
Measurement in watt.
Energy is the ability to do work.Power is the rate at which Energy is used
Energy Electrical Energy is theproduct of electrical powerand time.
It is the amount of time aload is on (i.e., current isflowing) time the amountof power used by the load(i.e. watts).
Measurement is watt-hour(Wh).
Electric Power and Electrical Energy
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21 2011
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Ohms Law, Power, and Energy 1st / 2011-2012 L. Valcos
tP =W
where,W = work done or energy converted in joulest = time in secondsP = power in joules/second or watts
01JUNE 21 2011
from,V = WQ and I =
Qt
tP =WP = V x I then
By Ohms Law, V = I x R
P = V x IP = I2 x R
P = V2R
Kilowatt-Hour (kWh)1 Joule = 1 watt x second or 1 J = 1 W x S
1 J = 1 W x S 1 kW1000 W1 h
3600 S
1 J = 13.6 x 106 kWh
1 kWh = 3.6 MJ
Horsepower (unit or mechanical output power)1 Hp = 746 Watts = 0.746 kW
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
x timePercent Power Efficiency, y
y = WoutWin =PoutPin x time
Pin% y =Pout x 100%
where,
Pout = heat energyPin = mechanical energy
Overall Efficiency = y1 x y2 x y3 which is always less than thesmallest efficiency.
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos
01JUNE 21, 2011
Thank You forlistening!
Lets discuss some sample problems relating to Ohms law, Electric Power andElectrical Energy
TOPIC TITLE SY / TERM OF EFFECTIVITY PREPARED BY#Foundation of DC Concepts, Ohm's Law, Power and Energy 3rd / 2013-2014 L. Valcos