An induction furnace is an electrical furnace that uses induction heating to melt metals. It provides a clean and efficient melting process compared to other methods. Induction furnaces range in size from less than one kilogram capacity up to 100 tonnes, and are used to melt metals like iron, steel, copper and aluminum. Their advantages include precise temperature control and preventing loss of alloying elements during melting.

1. Induction furnaces
The large scale application of electromagnetic induction has become very
c ommonplac e in today’s manufac turing industries. Many c omponents are heated
in very large ovens or furnaces to several thousand degrees Celsius.
A simple induction furnace where the object being heated is placed inside a
copper coil that carries a high frequency AC current and cooling water within the
tube
They range in use from the small, domestic furnaces used for heating, to
annealling (heat treating) metal parts, hardening metals, cap sealing,
heat shrink fitting and wire stripping. Even the de-gassing of cathode ray
tube components is done by induction heating. The induction furnace is
also used to heat small items to weld the parts together in router bits
(used in woodworking).
Applications of Mutual Induction...

2. 1. An induction furnace is an electrical furnace
in which the heat is applied by induction
heating of metal. The advantage of the induction
furnace is a clean, energy-efficient and well-controllable
melting process compared to most
other means of metal melting. Most
modern foundries use this type of furnace and
now also more iron foundries are replacing
cupolas with induction furnaces to melt cast
iron , as the former emit lots of dust and other
pollutants Induction furnace capacities range
from less than one kilogram to one hundred
tonnes capacity and are used to melt iron
and steel, copper, aluminium and precious
metals. Since no arc or combustion is used, the
temperature of the material is no higher than
required to melt it; this can prevent loss of
valuable alloying elements .The one major
drawback to induction furnace usage in a
foundry is the lack of refining capacity; charge
materials must be clean of oxidation products
and of a known composition and some alloying
elements may be lost due to oxidation (and must
be re-added to the melt).

3. 2. A fluorescent lamp or a fluorescent tube is a
low pressure mercury-vapour gas discharge lamp
that uses fluorescence to produce visible light. An
electric current in the gas excites mercury vapour
which produces short-wave ultraviolet light that
then causes a phosphor coating on the inside of
the bulb to glow. A fluorescent lamp converts
electrical energy into useful light much more
efficiently than incandescent lamp. The luminous
efficacy of a fluorescent light bulb can exceed
100 lumens per watt, several times the efficacy
of an incandescent bulb with comparable light
output.

4. 3. A metal detector is an electronic instrument which detects the presence of metal nearby.
Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects
buried underground. They often consist of a handheld unit with a sensor probe which can be
swept over the ground or other objects. If the sensor comes near a piece of metal this is
indicated by a changing tone in earphones, or a needle moving on an indicator. Usually the
device gives some indication of distance; the closer the metal is, the higher the tone in the
earphone or the higher the needle goes.
4. Induction cooking heats a cooking vessel with induction heating, instead of infrared
radiation from electrical wires or a gas flame as with a traditional cooking stove. For all models of

5. induction cooktop, a cooking vessel must be made of a ferromagnetic metal such as cast iron or
stainless steel or at least compounded with a steel inlay. Copper, glass and aluminium vessels
can be placed on a ferromagnetic interface disk which enables these materials to be used.
In an induction cooker, a coil of copper wire is placed underneath the cooking pot. An alternating
electric current flows through the coil, which produces an oscillating magnetic field. This field
induces a magnetic flux with a resulting eddy current in the pot equivalent to the electric
current in the coil. Eddy current in the metal pot produces resistive heating which heats the food.
While the current in the coil is large, it is produced by standard household voltage supplies.
Coefficient of mutual induction
It is a measure of the induction between two circuits; the ratio of the
electromotive force in a circuit to the corresponding change of current in a
neighbouring circuit; usually measured in henries.
Coefficient of mutual induction of two coils is numerically equal to the
amount of magnetic flux linked with one coil when unit current flows
through the neighbouring coil.
Now, the emf induced in the coil is given by
If dI/dt = 1, then =-M*1 or M =-
Hence coefficient of mutual induction of two coil is equal to the e.m.f.
induced in one coil when rate of change of current through the other coil is
unity.
Units S.I Unit of L=1Volt/1Amp/sec=1Henry

6. The SI unit of M is Henry, when a current change at the rate of one
ampere/sec in one coil induces an e.m.f. of one volt in the other coil.
Self Induction
When a time-dependent i.e. a varying current flows through a coil, the flux through the coil )due to the
magnetic field produced by current in it) will keep on changing. Hence an induced e.m.f. will be
produced in it. This process is called self induction.
For any given coil it is found that , where L is constant for the given coil.
The quantity L depends on the geometry of the coil and is called Coefficient of Self Inductance.
S.I Unit of L = 1 Volt / 1 Amp / sec = 1 Henry
Note : 1 Volt / Amp = 1 Ohm
1 Henry = 1 Ohm ´ sec
Mutual Induction
If two coils are kept close to each other and if a varying current flows through one of them then the
intensity of the magnetic field intensity () due to the current will vary. Hence flux through the other coil
will keep on changing with time; therefore an e. m. f. will be induced in the other coil. For any given
combination of coils it is found that , where M is constant and is called the Coefficient of Mutual
Inductance of the given arrangement of the given coils. The quantity M, like L, also depends on the
geometry of coils and their arrangements.
S.I Unit of M = 1 henry.
Diff...........
if an emf is induced in a coil due to the current flowing through itself is called SELF INDUCTANCE. on
the other hand if an emf is induced on another coil due to the current flowing through the previous coil
then it is called MUTUAL INDUCTANCE. suppose there are two coils A and B a current is flowing
through A. now if the flux produced due to this current induce an emf on the same coil A, then it is SELF
INDUCTANCE, and if it produce emf on B, then it is MUTUAL INDUCTANCE due to coil A.