This presentation contains information about some basic electrical parameters such as Voltage, Current, EMF, PD, Electric Power, Energy Ideal & Practical Sources, Types of Resistance, Heating Effect, Magnetic effect & Chemical effect of Electric Current etc.

1. Basic Electrical
Parameters
Mr. C D Patil
Dept. of EE

2. Definition of Basic Terms
• Current – Flow of electrons is known as
Electric Current
Current has 2 types
1. Alternating Current
2. Direct Current
• Frequency – Number of cycles completed in
one second.
In India, supply frequency is 50 Hz.

3. Definition of Basic Terms
• Electromotive Force (EMF) :- The electrical
force which causes the electrons to move or
flow.
• Potential Difference (PD) :- The difference in
Potential is known as Potential Difference.

4. Difference Between AC & DC

5. Type of Sources

6. Type of Sources
• 1. Ideal Voltage Source :-
A voltage source is a two-
terminal device whose
voltage at any instant of time
is constant Such a voltage
source is called an Ideal
Voltage Source and have
zero internal resistance.
• Vout = Vs
Voltage Source

7. Type of Sources
• 2. Practical Voltage Sources:-
Sources having some amount
of internal resistances are
known as Practical Voltage
Source.
• Due to this internal
resistance; voltage drop takes
place, and it causes the
terminal voltage to reduce
• Vout = Vs- I*Rs
Voltage Source

8. Type of Sources
Voltage Source
Ideal Voltage Source Practical Voltage Source

9. Type of Sources
Current Source
1. Ideal Current Source:
• An ideal current source is a
two terminal device which
supplies constant current
irrespective of
load resistance.
• The value of current will be
constant with respect to time
and load resistance.
• Here internal Resistance is
infinity.

10. Type of Sources
Current Source
2. Practical Current Source:
• A practical current source is
a two terminal device
having some resistance
connected across its
terminals.
• The value of current will be
reducing nature with respect
to time and load resistance.
• Here internal Resistance is
present

11. Electrical Work
• It is a workdone to transfer a charge from one
point to other point.
• Workdone= Force x Distance
W= F x D
• Unit of Workdone is Joule.

12. Electrical Power (P)

13. Electrical Energy (E)
• It is product of Electric Power & Time
• E = P x t
• Its unit is Watt-Hour

14. Resistance (R)
• Resistance is a measure of the opposition to
current flow in an electrical circuit
• Resistance is measured in ohms(Ω).

15. Resistivity (ρ)
• The electrical resistivity
is the electrical resistance
per unit length and per
unit of cross-sectional
area at a specified
temperature.
• Its symbol is (ρ) (rho)
• Its unit is ohm-m (Ω-m)

16. Conductivity (σ)
• It is the ability to conduct electricity through
given material.
• the SI unit of conductivity is Siemens per
meter (S/m) or mho and is usually represented
by Greek letter sigma, σ, and its formula is
given as;

17. Effect of Temperature on Resistance
• The electrical resistance changes with the
change of temperature.
• The resistance does not only increase with the
rise in temperature but it also decreases in
some cases.

18. Effect of Temperature on Resistance
• The resistance of all pure metals increases linearly
with increase in temperature over a limited
temperature range.
• The resistance of all metals such as tungsten, copper,
aluminum etc. increases linearly with increase in the
temperature over a limited temperature range. For e.g.
the resistance of copper is 100Ω at 0°c then it
increases linearly up to 100°c. At a temperature of -
234.5°c the resistance of copper is almost zero as
shown in the figure.
• Hence Pure metal have positive temperature
Coefficient of Resistance.
1. Effect of Temperature on Metal

19. Effect of Temperature on Resistance
• The resistance of semiconductor, Insulator, and
decrease with increase in temperature.
• At zero temperature, the semiconductor behaves as a
perfect insulator. As the temperature increases, some
of the electrons acquire energy and become free for
conduction.
• Hence, conductivity increase and resistance decrease
with increase in temperature.
• Semiconductor has negative temperature coefficient
of resistivity therefore since with the increase in the
temperature the resistance decreases.
2. Effect of Temperature on Semiconductor, Insulator

20. Types of Resistors
Resistors
Linear Resistor
Fixed
Resistor
Carbon
Composition
Resistor
Wire-
Wound
Resistor
Metal Film
Resistor
Variable
Resistor
Potentiometer Rheostat Trimmer
Non- Linear Resistor
Thermistors LDR

21. Types of Resistors
• Linear Resistor- The resistors whose value changes with the applied
temperature and voltage, are called linear resistors.
• Non- Linear Resistor- Non-linear resistors are those types of
resistors where the electric current flowing through it changes with
the exchange in applied voltage or temperature
• Fixed Resistor - Fixed resistors are resistors with a specific value.
• Variable Resistor– The value of resistance can be changed according
to requirement.

22. Types of Resistors
• Carbon resistors are mainly made of
carbon clay composition covered with a
plastic case. The lead of the resistor is
made of tinned copper.
• The main advantages of these resistors are
that they are readily available, low cost,
and they are very durable.
• The main disadvantage of carbon
composition resistors is that they are very
temperature sensitive.
• These resistors are also available in a wide
range of values, from as low as 1 Ω to as
high as 22 Mega Ω.
• It is used in power supplies and welding
controls
1. Carbon Composition Resistor

23. Types of Resistors
• Wire wound resistors are commonly made by
winding a metal wire, usually nichrome, around a
ceramic, plastic, or fiberglass core. The ends of
the wire are soldered or welded to two caps or
rings, attached to the ends of the core. The
assembly is protected with a layer of paint,
molded plastic, or an enamel coating baked at high
temperature. These resistors are designed to
withstand unusually high temperatures of up to
450 °C.
• It is used in high power applications like
transducers and televisions.
• It is also used as Temperature Sensors.
2. Wire Wound Resistor

24. Types of Resistors
• Metal film resistors have a thin metal layer as
resistive element on a non-conducting body.
• The desired value of resistance of metal film
resistor or carbon film resistor can easily be
obtained by either trimming the layer of the
thickness or by cutting helical grooves of
suitable pitch along its length as shown in fig.
• Metallic contact cap is fitted at both ends of
the resistor. The caps are in contact with the
conductive film or helical grooves. The lead
wire is welded to the end caps.
• It is used in active filters or bridge circuits.
3. Metal Film Resistor

25. Types of Resistors
• A potentiometer is a three-terminal resistor with a
sliding or rotating contact that forms an
adjustable voltage divider. If only two terminals
are used, one end and the wiper, it acts as
a variable resistor or rheostat.
• Potentiometers consist of a resistive element, a
sliding contact (wiper) that moves along the
element, making good electrical contact with one
part of it, electrical terminals at each end of the
element, a mechanism that moves the wiper from
one end to the other, and a housing containing the
element and wiper.
• Potentiometers are commonly used to control
electrical devices such as volume controls on
audio equipment.
4. Potentiometer

26. Types of Resistors
• Rheostat is a type of variable resistor, whose
resistance can be changed so as to change the
amount of current flowing through a circuit.
• It has two terminals, out of which one is fixed and
the other one is a moving terminal. Some rheostats
have three terminals just like potentiometer,
although only two terminals are used (Only one of
the two fixed terminals and the moving terminal
are used).
• It is used in Speed control circuits for motors,
heaters and ovens.
5. Rheostat

27. Types of Resistors
• A trimmer potentiometer, also known as a trim pot,
is a type of variable resistor or adjustable
potentiometer that can adjust, tune, and calibrate
circuits. These trimmer resistors are often used to
initially calibrate equipment after manufacturing.
• It is used in radio and television receivers, in
the intermediate frequency (IF), oscillator and radio
frequency (RF) circuits.
6. Trimmer

28. Types of Resistors
• The word thermistor means a thermal resistor. Its
resistance value changes with the change in the
temperature.
• A thermistor is a resistance thermometer, or a
resistor whose resistance is dependent on
temperature. The term is a combination of “thermal”
and “resistor”. It is made of metallic oxides, pressed
into a bead, disk, or cylindrical shape and then
encapsulated with an impermeable material such as
epoxy or glass.
• Most thermistors have a negative temperature
coefficient which means its resistance will fall down
when the temperature increases.
• These are normally made of semiconductor materials.
Resistance up to a few mega ohms can be obtained
from thermistors.
• Thermistors are used as temperature sensors.
7. Thermistors

29. Types of Resistors
• A Light Dependent Resistor (or LDR) will vary in
resistance depending on the intensity of light falling
on it. This is made of cadmium sulfide which
contains a small number of electrons when it is not
illuminated.
• When a light ray falls on it, electrons get ejected and
hence the conductivity of it increases. Hence, it offers
low resistance when light falls on it and offers high
resistance in the dark.
• In the dark, a LDR can have a resistance as high as
several mega ohms (MΩ), while in the light, a LDR
can have a resistance as low as a few hundred ohms.
• It is used in alarm clocks, street lights, light intensity
meters, camera light meters etc.
8. LDR (Light Dependant Resistor)

30. Heating Effect of Electric Current
• When current flows through a conductor, heat energy is generated in the
conductor.
The heating effect of an electric current depends on three factors:
1. The resistance, R of the conductor. A higher resistance produces more heat.
2. The time, t for which current flows. The longer the time the larger the
amount of heat produced
3. The amount of current, I. the higher the current the larger the amount of
heat generated.
• Hence the heating effect produced by an electric current, I through a
conductor of resistance, R for a time, t is given by H = I2Rt. This equation
is called the Joule’s equation of electrical heating.

31. Heating Effect of Electric Current
 Applications of heating effect of electric current
1. In electrical heating
A. Electric Cookers- electric cookers turn red hot and the heat energy produced is absorbed by the
cooking pot through conduction.
B. Electric Heaters- radiant heaters turn red at about 9000C and the radiation emitted is directed into
the room by polished reflectors.
C. Electric Kettles- the heating element is placed at the bottom of the kettle so that the liquid being
heated covers it. The heat is then absorbed by water and distributed throughout the whole liquid
by convection.
D. Electric Irons- when current flows through the heating element, the heat energy developed is
conducted to the heavy metal base raising its temperature. This energy is then used to press
clothes. The temperature of the electric iron can be controlled using a thermostat.

32. Heating Effect of Electric Current
 Applications of heating effect of electric current
2. In lighting appliances
A. Filament Lamps- it is made of a tungsten wire enclosed in a glass bulb from which air has been
removed. This is because air would oxidize the filament. The filament is heated up to a high
temperature and becomes white hot. Tungsten is used due its high melting point; 34000 The bulb
is filled with an inactive gas e.g. argon or nitrogen at low pressure which reduces evaporation of
the tungsten wire. However, one disadvantage of the inert gas is that it causes convection currents
which cool the filament. This problem is minimized by coiling the wire so that it occupies a
smaller area which reduces heat loss through convection.
B. Fluorescent lamps- these lamps are more efficient compared to filament lamps and last much
longer. They have mercury vapour in the glass tube which emits ultraviolet radiation when
switched on. This radiation causes the powder in the tube to glow (fluoresce) i.e. emits visible
light. Different powders produce different colors.

33. Heating Effect of Electric Current

34. Magnetic Effect of Electric Current
• When a current flows through
the conductor, a magnetic field
will produce across that
conductor.
• Applications- Electric Crane,
Electric Motor, Transformer,
Electromagnet etc.

35. Chemical Effect of Electric Current

36. Thank You!!!