Reading Material (SELF-INDUCTION)

SELF-INDUCTANCE

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What is self
induction?

It is a phenomenon
where a varied
current circuit has an
induced E.M.F in it
due to the variation in
its own magnetic
field.

2

3

When the switch is closed, there
is current flow through the
circuit.

It The The flux
produces current which is
an induced increased due to this
magnetic in time current
field (zero to will also
through maximum). increase in
the time
current
circuit. 4

When the This means And the
current in that the direction
the coil is direction of induced
increasing, of the current is
the self- induced opposing
E.M.F is
induced the
E.M.F opposite to direction
produced the applied
in the coil of the
will oppose voltage. current
produced
the by the
current. battery.

5

Self induced

E.M.F is always

proportional to

∝ − the time for the

rate of change of

the source

current.

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SELF INDUCTANCE, L

Ratio of the self induced E.M.F

01 to the rate of change of

current in the coil.

02 SI Unit :
Henry ( H )

03 = − Where
= Induced E.M.F , Volt (V)

L = Self-inductance, Henry (H)

= Rate of Source current,

Ampere per second (A s-1)

Inductance, L

depends on



Coil

10

Solenoid

where
L : self inductance, Henry (H)
N : number of turns
μo: permeability of free space (4π × 10–7 T m A–1)
A : cross sectional area of the solenoid, meter square (m2)
l : length of the solenoid, meter (m)
n : number of turns per unit length, per meter (m-1)

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( = )

2 3
1

1 A conductor 2 The flux 3 The

(iron core) is inside the inductance

placed inside solenoid will will increase.

the solenoid. increase.

As the conductor is placed, the
inductance is;

or

where
μ : permeability of the material
μr : relative permeability
μ0 : permeability of free space, (4π × 10–7 T m A–1)

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