Electrical fundamentals Part 1

Subhodeep Krishna Deb
When a copper wire is kept in motion in any magnetic
field then current is generated in the copper wire.
And the current generated opposes the cause that creates
the current.

BASIC ELECTRICAL DEFINITIONS
LAWS OF ELECTRICITY
TERMS FAMILIARIZATION
ELECTRICAL UNITS

SWITCH
SYSTEM
RELAY
SYSTEM
MOTOR
SYSTEM
GENERATOR
SYSTEM

Charge …
Charge is measured in coulombs and
is the amount of “electricity” present
(or flowing).
Charge can be positive or negative.
Like charges repel each other & Unlike charges attract each other.
Current move from positive charge to negative charge.
Charge moves about and may be stored.
It is denoted by “Q” and is measured in “coulombs”.

 Current is a flow of charge; the rate of
Movement of charge through a system.
 It is analogous to the flow of water (in liters /s).
 It is measured in amps; An amp is quite big.
 A.C. is alternating current, where the current flows first
one way then the other (repeatedly).
 D.C. is Direct Current where a current flows in the same
direction at all times.
Current …

 Voltage is electrical “pressure”.
 It is analogous to the pressure of a water flow (say like the
height of a reservoir).
 Voltage is measured in volts; and is denoted by “V”.
There can be positive volt or negative volt.
Voltage …

 Energy is a measure of work done.
 Electrical energy is most commonly known as electricity.
 Electrical energy refers to the flow of power or the flow of charges
along a conductor to create energy.
Energy…

 Power is the work done per unit time.
 Thus if a battery contains so much energy it can power something
for a particular time.
 Electric power is defined as the rate at which electrical energy is
transferred by an electric circuit.
 The SI unit of power is the watt.
 It is given by the formula: Voltage (V) * Current (I).
Power…

P
O
W
E
R
D
I
S
T
R
I
B
U
T
I
O
N

 Frequency is the number of
occurrences of a repeating event
per unit time.
The period is the duration of one cycle in a repeating event, so the
period is the reciprocal of the frequency.
 Its unit is cycles per sec. or Hertz.
 It is applicable only for AC current only.
Low Frequency
High FrequencyFrequency…

The term Open circuit may refer to:
 An open circuit has no current flowing through it.
 The voltage across the open part is infinity.
 Open-circuit voltage, the difference of electrical potential between two
terminals of a device when there is no external load connected.
 An electric circuit is an "open circuit" if it lacks a complete path
between the positive and negative terminals of its power source.
Open circuit…

The term Closed circuit may refer to:
 No extra voltage in the circuit.
 A closed circuit has current flowing through it.
 An electric circuit is an “closed circuit" if it has a complete path
between the positive and negative terminals of its power source.
Switch Closed
Closed circuit…

ELECTRICAL DEFINITIONS
LAWS OF ELECTRICITY
TERMS FAMILIARIZATION
ELECTRICAL UNITS

 The fingers of the right hand are curled
to match the curvature and direction of the
motion or the magnetic field. The thumb
indicates the direction of the vector.
 The thumb shows the direction of
current through the conductor.
 The fingers show the direction of the
magnetic field.
Fleming’s Right – hand Rule

The current through a conductor between
two points is directly proportional to the
potential difference or voltage across the two
points, and inversely proportional to the
resistance between them.
The mathematical equation that describes
this relationship is:
R = V
I
Ohm’s Law

At every instant of time the sum of the currents
flowing into any node of a circuit must equal the
sum of the currents leaving the node.
Similarly, at any instant the algebraic sum of all
the currents at any circuit node is zero.
this relationship is: I1 + I2 + I3 = I4
Kirchoff’s Current Law

The principle of conservation of energy implies that the directed sum of the
electrical potential differences (voltage) around any closed circuit must be zero.
or
More simply, the sum of the emfs in any closed loop is equivalent to the sum
of the potential drops in that loop.
or
The algebraic sum of the products of the resistances of the conductors and the
currents in them in a closed loop is equal to the total emf available in that
loop.
this relationship is: V1 + V2 = V3 + V4
Kirchoff’s Voltage Law

 Also known as the Motor Rule this is a way of
determining the direction of a
force on a current carrying conductor in
a magnetic field.
 The thumb, the first and the second
fingers on the left hand are held so
that they are at right angles to each other.
Fleming’s Left – hand Rule
If the first finger points in the direction of the magnetic field and the
second finger the direction of the current in the wire, then the thumb will
point in the direction of the force on the conductor.

 If the first finger points in the direction of the magnetic field and the thumb
in the direction of the motion of the conductor then the second finger will point
in the direction of the induced emf in the conductor.
Fleming’s Right – hand Rule
 Also known as the Generator Rule this is a
way of determining the direction of the
induced emf of a conductor moving in a
magnetic field.
 The thumb, the first and the second fingers
on the right hand are held so that they are at
right angles to each other.

 Linear Circuits : These circuits are
those whose parameters do not change
with the current and voltage in the circuit.
 Non-Linear Circuits: These circuits are
those whose parameters keep changing with
the current and voltage in the circuit.
 Bilateral Network: These are the network whose characteristics does not depend on the
direction of the current, voltage in the circuit.
 Unilateral Network: These are the network whose characteristics depend on the
direction of the current, voltage in the circuit, and sometimes work for only one direction
of current.
 Active Network: The linear electrical circuit which has one or more emf cells or sources.
 Conductor: All the materials that allows easy flow of current through it are conductors.

 Insulators: Materials that does not allow
flow of current through it, ex. Rubber, wood.
Passive Network: The linear electrical
circuits which has no emf and battery
sources in the circuit.
 Node : It is the point in any electrical
circuit where two or more current carrying
conductors meet.
 Branch: It is part from the current carrying conductor which divides
the current into respective distribution.
 Loop : It is the closed circuit, in which amount of current flowing remains the
same.
 Mesh: It is the closed circuit which has no loops in it.

Parameter Symbols Units
Charge Q Coulomb
Current I Amphere
Voltage V Volt
Power P Watt
Frequency f Hertz

For related assistance & service:
subhodeepkrishnadeb@gmail.com

Electrical fundamentals Part 1

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