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1. ELECTRIC CURRENT

2. • Electric Current is the rate of flow of electrons in a
conductor. The SI Unit of electric current is the Ampere.
Introduction
• Electrons are negatively charged particles; hence when they
move, a number of charges moves, and we call this
movement of electrons as electric current

3. • It should be noted that the number of electrons that are able to
move governs the ability of a particular substance to conduct
electricity.
• Some materials allow the current to move better than
others. Based on the ability of the material to conduct electricity,
materials are classified into conductors and insulators.
Cont.…

4. • Conductors: are materials that allow the free flow of
electrons from one particle to another.
• Conductors allow for charge transfer through the free
movement of electrons. The flow of electrons inside the
conducting material or conductor generates an electric
current.
Conductors

5. • The force that is required to drive the current flow through
the conductor is known as voltage.
• Examples of conductors: Human body, aqueous solutions of
salts and metals like iron, silver and gold.
Cont.…

6. • Insulators: are materials that restrict the free flow of
electrons from one particle to another.
• The particles of the insulator do not allow the free flow of
electrons; subsequently, the charge is seldom distributed
evenly across the surface of an insulator.
• Examples of Insulators: Plastic, Wood and Glass
Insulators

7. How is current generated?
• Current can be generated when there is potential difference
between two points on a circuit. Potential difference is like a
driving force that provides energy for a charge to move.
• Potential difference is just like an energy provider for
charge to move in a circuit. Higher the potential difference
more is the energy the charge carries while moving.

8. How is current generated?

9. Prerequisites for the Current to Flow in a Conductor
• Some of the prerequisites for the electric current to flow in a
conductor are discussed here.
• The circuit includes an energy source (a battery, for instance)
that produces voltage. Without voltage, electrons move
randomly and are undirected; hence current cannot flow.
Voltage creates pressure on the electrons, which channelizes
them to flow in a single direction.

10. Cont. …
• The circuit forms a closed conducting loop through which
electrons can flow. A circuit is said to be closed or complete
when a switch is turned ON.

11. Properties of Electric Current
• After we define electric current, let us learn the properties of
electric current. Electric current is an important quantity in
electronic circuits. We have adapted electricity in our lives
so much that it becomes impossible to imagine life without
it. Therefore, it is important to know what is current and the
properties of the electric current.

12. Cont. ..
• We know that electric current is the result of the flow of electrons.
The work done in moving the electron stream is known as electrical
energy.
• Electrical energy can be converted into other forms of energy such as
heat energy, light energy, etc.
• For example, in an iron box, electric energy is converted to heat
energy. Likewise, the electric energy in a bulb is converted into light
energy.

13. Cont. ..
• There are two types of electric current known as alternating current (AC)
and Direct Current (DC)
• The direct current can flow only in one direction, whereas the alternating
direction flows in two directions.
• Direct current is seldom used as a primary energy source in industries. It
is mostly used in low voltage applications such as charging batteries,
aircraft applications, etc.

14. Cont. ..
• Alternating current is used to operate appliances for both
household and industrial and commercial use.
• The electric current is measured in ampere. One ampere of
current represents one coulomb of electric charge moving
past a specific point in one second.
1 ampere = 1 coulomb / 1 second

15. Cont. ..
• The conventional direction of an electric current is the
direction in which a positive charge would move.
• Henceforth, the current flowing in the external circuit is
directed away from the positive terminal and toward the
negative terminal of the battery.

16. Ohms and Volts
• Scientists know that there are ways of measuring electrical
quantities. One of these is coulombs per second, a measure
of the flow of electrons through a metal conductor or wire.
• A current of one coulomb per second equals one ampere

17. Cont. ..
• Even materials that conduct electricity resist the flow of
electrons. The unit of electrical resistance is an ohm.
• The pressure needed to make one coulomb per second
(one ampere) flow through a conductor having a
resistance of one ohm is one volt.

18. Ohm’s law
• Ohm's Law explains the relationships between voltage (E),
resistance (R), and current (I).
• In two circuits of equal voltage, the current will be
proportionately greater in the circuit of lower resistance. In
circuits of equal resistance, the current flowing will be
directly proportional to the voltage applied.

19. Cont. ..
• Hence Ohm’s Law states that “Electric current is
proportional to voltage and inversely proportional to
resistance ”
• i.e.
•
• Also,
 
 
 
E Volts
I Amperes
R Ohms

E
E IR or R
I
 

20. Cont. ..
• One of the most common electrical measurements you’ll
use is the watt, a unit of electrical power.
• Power (Watts) = E (Volts) x I (Amperes).

21. Visualizing Electric Current
• To gain a deeper understanding of what an electric
current is and how it behaves in a conductor, we can use
the water pipe analogy of electricity. Certainly, there are
some limitations but they serve as a very basic
illustration of current and current flow.

22. • We can compare the electric current to the water flowing through
the pipe.
• When pressure is applied to one end of the pipe, the water is forced
to flow through the pipe in one direction.
• The amount of water flow is proportional to the pressure placed on
the end. This pressure can be compared to the electromotive force.
Water Pipe Analogy of Electricity

24. Effects of Electric Current
• Let us learn various effects of electric current. When a current
flows through a conductor, there are a number of signs which tell
if a current is flowing or not. Following are the most prominent
signs.
• When an electric current flows in a circuit it can have one or
more of the following three
effects: heating, magnetic or chemical.

25. Heating Effect of Electric Current
• When an electric current is passed through a conductor, it
generates heat due to the hindrance caused by the
conductor to the flowing current. The work done in
overcoming the hindrance to the current generates heat in
that conductor.
• The heating effect is given by the following equation
• H=I2RT

26. Cont. ..
The heating effect depends on the following factor:
• The time ‘t’ for which the current flows. The longer the current
flows in a conductor more heat is generated.
• The electrical resistance of the conductor. Higher the resistance,
the higher the heat produced.
• The amount of current. The larger the amount of current higher
the heat produced.

27. Cont. ..
• If the current is small then the amount of heat generated
is likely to be very small and may not be noticed.
However, if the current is larger then it is possible that a
noticeable amount of heat is generated.

28. Applications of Heating Effect of Electric Current
• The heating effect of electric current is widely used in our day-
to-day life.
• The electric iron, kettle, toaster, heater, etc. are used as
alternatives to the conventional methods of cooking and laundry.
• The same is used in electric bulbs which is the alternative of
conventional lamps.

29. Cont. ..
• These devices have revolutionized the world over the years.
• In this section, we will discuss the concept of the heating
effect of electric current and its applications.

31. ELECTRIC IRON:
• Mica is an insulator that is placed between the metal
part and the coil in an iron.
• The coil becomes heated with the passage of current
which is then transferred to the metallic part
through mica.
• Finally, the metal part becomes heated which is then
used for ironing clothes.

32. ELECTRIC BULB:
• Electric bulb contains a thick metallic wire made up
of tungsten metal. The metal is kept in an inert
environment with a neutral gas or vacuum. When
current flows through the tungsten wire, it becomes
heated and emits light. Most of the electric power
drawn in the circuit from the electrical source is
dissipated in the form of heat and the rest is emitted
in the form of Light energy.

33. ELECTRIC HEATER:
• In an electric heater, high resistance nichrome
wire is used as a coil. The coil is wound on
grooves made up in ceramic material or China
clay.
• When the current flows in the coil, it becomes
heated, which is then used to heat cooking
vessels.

34. ELECTRIC FUSE:
• In any electrical instrument, due to sudden rise
of current, the instrument gets burnt down
which sometimes results in fire. A conducting
wire with low melting point is connected in
series with the circuit to avoid this type of
accident. When the current rises, the wire melts
due to excessive heating, thus breaking the
electrical circuit.

35. For harnessing the heating effect of electric current, the
element of appliances is required to have high melting points
to retain more heat.
Keep in Mind !!

36. Chemical Effect of Electric Current
• When an electric current passes through a solution, the
solution ionizes and breaks down into ions. This is because a
chemical reaction takes place when an electric current
passes through the solution.
• Depending on the nature of the solution and the electrodes
used, the following effects can be observed in the solution:

37. Cont. ..
 Change in the color of the solution
 Metallic deposits on the electrodes
 A release of gas or production of bubbles in the solution
 Electroplating and electrolysis are the applications of the
chemical effect of electric current.

38. Magnetic Effect of Electric Current
• Another prominent effect that is noticeable when an electric current
flows through the conductor is the build-up of the magnetic field.
• We can observe this when we place a compass close to a wire carrying
a reasonably large direct current, and the compass needle deflects.
The magnetic field generated by a current is put to good use in a
number of areas.
• By winding a wire into a coil, the effect can be increased, and an
electromagnet can be made.

39. Cont. ..
• A magnetic field is a force field that is created by magnetic
dipoles and moving electric charges, and it exerts a force on
other nearby moving charges and magnetic dipoles.
• Magnetic Field is a vector quantity because it has both
magnitude and direction.

40. Magnetic Field Lines
• A magnetic field line or lines of forces shows the strength of a magnet and
the direction of a magnet’s force. It was discovered by Michael Faraday to
visualize the magnetic field.
Direction of Field Lines
• Magnetic field lines are directed from the south pole to the north pole
inside the magnet and from the north pole to the south outside the
magnet.
• The direction of the magnetic field gets reversed if the direction of electric
current changes.

41. Cont. ..
Strength of Magnetic Field Lines
• A straight current-carrying conductor has a magnetic field in the shape
of concentric circles around it. Magnetic field lines can visualize the
magnetic field of a straight current-carrying conductor.
• The direction of a magnetic field produced due to a current-carrying
conductor relies upon the same direction in which the current is flowing.

42. Let us understand Magnetic Effect of Electric Current
using a simple experiment:
• Suppose a straight current-carrying conductor is
hung vertically, and an electric current is flowing
from north to south, i.e. from up to down.
• In this situation, the direction of the magnetic field
will be clockwise. And if the same current is
flowing from south to north through the same
conductor, the direction of the magnetic field will
be anti-clockwise.

43. Cont. ..
• The direction of the magnetic field in
electric current through a straight
conductor can be represented by using
the Right-Hand Thumb Rule.

44. Right-Hand Thumb rule
• Assume that you are holding a straight current-carrying
conductor in your right hand such that the thumb points
towards the direction of the current.
• Then your fingers will wrap around the conductor in the
direction of the magnetic field lines.

45. Cont. ..
• The Right-Hand Thumb rule is also known as
Maxwell’s corkscrew rule. If we consider
ourselves driving a corkscrew in the current
direction, then the corkscrew’s direction is in
the direction of the magnetic field.

46. Magnetic Field Due to Flow of Current through a
Circular Loop
• The magnetic field produced in a circular
current carrying conductor is the same as
that of the magnetic field due to a straight
current-carrying conductor and the current-
carrying circular loop will behave like a
magnet

47. Cont. ..
• The magnetic field lines in a current-carrying circular loop
would be in the shape of concentric circles, and at the Centre
of the circular wire, field lines will become straight and
perpendicular to the plane of the coil.
• The direction of the magnetic field in a circular loop can be
recognized using the Right-Hand Thumb Rule

48. Magnetic Field due to flow of current in a Solenoid
• A solenoid is a tightly wound helical coil of wire whose
diameter is smaller than its length.
• The magnetic field produced by the current-carrying
solenoid is similar to a bar magnet. The magnetic field
produced inside a solenoid is parallel which is similar to a
bar magnet. One solenoid end behaves as a south pole, and
the other end behaves as a north pole.

49. Cont. ..
• The strong magnetic force produced by a
solenoid can be used to magnetize a
piece of magnetic material.
• The magnet so formed is known as an
electromagnet.

50. Direct Current
 Direct Current is the unidirectional flow of electric current.
The flow of current does not change periodically.
 In the case of direct current, the current flows in a single
direction at a steady voltage.
 Direct current power is widely used in low voltage
applications such as charging batteries and light aircraft
electrical systems.

51. Cont. ..
 A direct current can be obtained from an alternating current
using a rectifier. A rectifier contains electronic elements or
electromechanical elements that allow current to flow only in
one direction.
 Direct current can also be converted into alternating current
using a motor-generator set or an inverter.

52. Frequently Asked Questions – FAQs
• State Fleming’s right-hand rule.
• State Fleming’s left-hand rule.
• What would be the shape of the magnetic field lines in a circular current
carrying loop?
• State Right Hand Thumb Rule.
• What is the direction of Magnetic field lines?

55. 09/11/2022
Class 2
• Contents to be covered
1. Kirchhoff’s Current Law
2. Kirchhoff’s Voltage Law
3. Resistors in Series and Parallel
4. Voltage and Current Division

56. Tutorial 1

61. Assignment 01
• What is Electromotive Force ?
• What is Electromotive Force Formula ?
• What is the unit of EMF ?
• Difference between Electromotive Force and Potential Difference
• Can electromotive force be negative ?
• What is the difference between terminal voltage and EMF ?