1. TRANSFORMERS

2.  An electrical transformer is a static device which is used for the
transformation of AC electrical signal in one circuit to the electrical signal of
the same frequency in another circuit with a little loss of power

3. How do transformers work?
 The operation of transformer mainly works
on the principle of mutual inductance
between two circuits linked by a common
magnetic flux.
 A transformer is basically used for
transformation of electrical energy.
 Transformers consist of types of conducting
coils as primary winding and secondary
windings.
 The input coil is called the primary winding
and the output coil is called the secondary
winding of the transformer

4.  The windings are linked by an alternating magnetic field created in the
soft-iron core of the transformer.
 Transformers waste very little power so the power out is almost equal to
the power in.
 The primary coil and the secondary coil posses high mutual
inductances. If one of the coils is connected to the source of alternating
voltage, then an alternating flux will set up in the laminated core.
 This flux gets linked up with the other coil and an electromagnetic force is
induced, as per Faraday’s law of electromagnetic inductance.
 e = M di/dt Where e is induced EMF M is mutual inductance
 If the second coil is closed then the current in the coil is transferred from
primary coil of the transformer to the secondary coil.

5. Ideal power equation of transformer
 If the secondary coil is attached to a load that allows current to flow in the
circuit, electrical power is transmitted from the primary circuit to the
secondary circuit.
 Ideally, the transformer is perfectly efficient; all the incoming energy is
transformed from the primary circuit to the magnetic field and into the
secondary circuit. If this condition is met, the incoming electric power must
equal the outgoing power:
 Giving the ideal transformer equation

6.  Different Types of Transformers classified based on different criteria like
function, core, etc.
FUNCTIO
N
CORE BASED
ON
WINDINGS
ARRANGEME
NT OF THE
COILS
ACCORDING
TO USE
TYPE OF COOLING
Step-up Core type Two
winding
Cylindrical
type
Power
transformer
Natural cooling
Step-down Shell type Single
winding
Disc type Distribution
transformer
Oil immersed natural
cooled
Three
winding
Oil immersed natural
cooled with forced oil
circulation

7. Classification according to function:
Step-Up Transformer
 A step up transformer is the one in which the
primary voltage of the coil is lesser than
secondary voltage. A Step-up transformer can
be used for increasing voltage in the circuit.
Step-down transformer
 is used for reducing the voltage.
 The type of transformer in which the primary
voltage of the coil is greater than the secondary
voltage.
 Most power supplies use a step-down
transformer to reduce the dangerously high
voltage to a safer low voltage.

8.  The ratio of the number of turns on each coil, called the turn’s ratio
determines the ratio of the voltages.
 A step-down transformer has a large number of turns on its primary (input) coil
which is connected to the high voltage mains supply, and a small number of
turns on its secondary (output) coil to give a low output voltage.
 TURNS RATIO = (Vp / Vs) = (Np / Ns)
 Where, Vp = primary (input) voltage Vs = secondary (output) voltage Np =
number of turns on primary coil Ns = number of turns on secondary coil Ip =
primary (input) current Is = secondary (output) current.

9. POTENTIOMETERS
 A potentiometer (also known as a pot or potmeter) is defined as a 3
terminal variable resistor in which the resistance is manually varied to
control the flow of electric current.
 Principle of potentiometer:
 When a steady current flows through a wire of uniform cross section
the potential difference of unit length of the wire is constant
throughout the length of the wire across any two points if the wire is
directly proportional to the length of the wire.

10. advantages
 Used to measure internal resistance
 More sensitive compared to voltmeter
 The accuracy of the potentiometer can be increased by increasing the
length of the wire