Answer / ashli

mutual induction is the principle of transformer. on
applying dc on the primary wng there ll b no variation in
the flux linked with the secondary n primary windngs. ie no
emf induced in the secondary winding except at the time of
switching and so no output u get...v know that the wndg
resistance is low.. in normal case although we r applying a
high voltage, due to the self induced emf in primary wndg,
which opposes the applied voltage, the primary current is
limitted to a low value.. if the applied voltage is dc no
self inuced emf to oppose and hence leads to a heavy
primary current that causes burning out of primary windg

Answer / rajat singh, naveen kumar

When ac flows due to frequency emf is induced. But In case
of dc, frequency is zero so there will be no emf induced.
b'coz:
emf, e= 4.44 f*phi*N
and when, f=0
emf, e=0
So there will be no emf at primary as well at secondary
side.
Thats the reason transformer doesn't work on dc.

Answer / padmanabh thakur(geu)

for dc rate of change of flux is zero so there is no
induced emf in primary as well as in secondary

Answer / panks

ac means alternating current which is due to frequency,
without which emf will not get induced.

As per ur doubt, in case of DC, frequency is zero hence no
emf will be induced.There will be no emf on primary as well
as on secondary side due to which heavy primary current
leads to damage the primary winding & dc is constant due to
which no flux linkage changes will be there.

We r using the transformer for stepping up or down the
voltage, which is not possible in case of dc due to zero
emf.

Hence due to above reasons trafo doesn,t work on dc.

Answer / glen

in dc frequency is zero the coil becomes short in
transformer primary winding
xl=2phi f l
xl=0

Answer / boopathi

generally for inducing emf we need three factors
1.flux
2.conductor
3.relative motion between conductor and the flux
*while applying the dc supply to the transformer ,the
relative motion between the conductor and the flux will not
be there,so there is no chance for inducing emf...
*while applying the ac supply,due the current changing
form positive to negative it will act as a relative motion
between the conductor and the flux..so the change of flux
takes place and the emf will be induce..
*therefore,no emf will be induce while applying dc supply
to the transformer and it need an external source for
change of flux

Answer / mohamed sathik

mutual induction is the principle of transformer. on
applying dc on the primary wng there ll b no variation in
the flux linked with the secondary n primary windngs. ie no
emf induced in the secondary winding except at the time of
switching and so no output u get...v know that the wndg
resistance is low.. in normal case although we r applying a
high voltage, due to the self induced emf in primary wndg,
which opposes the applied voltage, the primary current is
limitted to a low value.. if the applied voltage is dc no
self inuced emf to oppose and hence leads to a heavy
primary current that causes burning out of primary windg

Answer / lsk.1

*when the dc supply is given to the transformer.
*no frequence is induced
*by the emf equation of a transformer.
*e=4.44f(BA)(VOLT)
*IF THE F=0.
*then the induced emf=o.
*so transformer cannot be in dc supply

Answer / abe thejo thomas

since transformer is a static machine,it requires a varying
voltage to produce induced emf.if dc is applied there wont
be any variation in the applied voltage,and hence no emf
will get induced

Answer / sunil parmar

for working of a transformer it needs flux linkage between
windings..and winding of the transformer has low reactance
so when DC is applied due to zero flux linkage circulating
current is produced on primary side of transformer and will
burn the wdg. if DC is applied continuously ...
and also frequency is zero in DC
so E=4.44*f*B*A
in DC f=0
so,E=o on secondary side......

plz vote for my answer..
for reply mail me at parmar20072008@yahoo.com

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