INVESTIGATORY PROJECT CLASS 12 PHYSICS

1. PRINCIPLE
It is based on the principle of mutual
induction that
is if a varying current is set-up in a
circuit then
induced e.m.f. is produced in the
neighboring
circuit. The varying current in a circuit
produce
varying magnetic flux which induces
e.m.f. in the
neighboring circuit.
CONSTRUCTION
transformer consists of a rectangular shaft
iron core made of laminated sheets, well
insulated from one another. Two coils p1 & p2
and s1 & s2 are wound on the same core, but are
well insulated with each other. Note that the
both the coils are insulated from the core, the
A

2. source of alternating e.m.f is connected to
p1p2, the primary coil and a load resistance R
is connected to s1 s2, the secondary coil
through an open switch S. thus there can be no
current through the sec. coil so long as the
switch is open. For an ideal transformer, we
assume that the resistance of the primary &
secondary winding is negligible. Further, the
energy loses due to magnetic the iron core is also
negligible. For operation at low frequency, we may
have a soft iron. The soft iron core is insulating
by joining thin iron strips coated with varnish to
insulate them to reduce energy losses by eddy
currents. The input circuit is called primary. And
the output circuit is called secondary.
An ideal voltage step-down transformer. The
secondary current arises from the action of the
secondary EMF on the (not shown) load impedance.

3. The ideal transformer as a circuit element.