Answer / ashraf majid

Ohm's Law holds good in both AC as well as DC,however, with
a slight modification in case of AC. In DC, the ratio of
voltage(V) across load(conductor)terminals to the current
(I) flowing through it,at any instant of time, always gives
the "RESISTANCE" of the load(conductor); while in AC, it
always gives "IMPEDANCE" of the load(conductor). However,
in both the cases the external physical conditions(such as
temperature , pressure,etc;) should remain same; otherwise
Ohm's Law will not hold good.
A transformer is a static machine which just transforms
(changes) the voltage levels on either side of its
connection. It does not generate any energy of its own. It
rather consumes some portion of energy inthe form of losses
(Copper loss & Iron loss). If we neglect these losses, then
power(energy) supplied to the transformer will always be
equal to the power(energy) drawn from it.In other words, a
transformer is a constant power machine, it has to keep
power on both sides same. Since power(P) is given by
P=V*I. So for changing voltage levels, it has to change the
current levels also.Here the valid expression would be
V*I=Constant and it has nothing to do with Ohm's Law. Ohm's
law has its own definition and holds good in its own
conditions, While as voltage transformation holds good in
its own conditions. These are two different things.
However, in any case Whatever voltage,AC or DC(from any
side of the transformer or any other source) is applied to
any load, Ohm's Law will hold good with the modifications
as described above in para 1.

Answer / shailesh nimkar

Ohm's law holds in both AC as well as in DC......
Ohms law state that at room temp the voltage is directly
praportional to current
and R is constant
but in case of transformer impedance is change from primary
to secondary so this relation not obey the situation
but the principle of transformer it transfer the energy
from one ckt to another ckt without changing frequency
means constant power in both side or equal power
power=v*i
so if v increase I decrease

Answer / ram_svepl

OHM'S LAW IS APPLICABLE YO BOTH AC AND DC.
IN TRANSFORMER THE POWER IS TRANSFERRED FROM PRIMARY TO
SECONDARY SUCH THAT FREQUENCY AND POWER REMAIN UNALTERED IN
SECONDARY AND PRIMARY.

SO IN ORDER TO MAINTAIN SAME POWER

V1*I1=V2*I2(ASSUME SAME PF ON BOTH SIDES)

SO IF V2 INCREASES THEN I2 SHOULD DECREASE CORROSPONDINGLY.

Answer / javed

ohm law is applicable for both ac and dc
according to ohm law if we pass current through any
resistive ckt, the ratio of change in current directly
proportional to change in voltage
V = I*R (where R is constant)
but in case of inductive ckt (like transformer), inductance
of the ckt always try to oppose the change in current, but
in case of dc inductance of the ckt is zero, so in case of
AC, voltage vary nonlinerly with change in current.
(remember ohm law in not applicable for inductive ckt it is
only applicable for resistive ckt)

Answer / vidhya

OHMS law holds good in both dc and ac for only SIMPLE
circuits...its not applicable for mutually coupled circuits
and all...

Answer / manoj k mishra

all the answers above are good to read.........

" but you need to understand the diffrence between voltage
and voltage dorp"

Answer / karthi

The ohms law deals the theory only when the steady current
is flowing at constant temparature through the conductor.

Answer / chiranjit mondal

question(2nd part)is not clear

Answer / priya

it is not volatge is equal to current. voltage and current
on dependent on a proportionality factor. this factor
determines their relationship

Answer / akhtar hussain

yes it is true that ratio of currents is inversilly proportional to the voltage but main reason is that in only one circuit of transformer the ohms law holds but while reffering both the circuits ohms law does not hold because as we supply ac vo V to the primary side then alternating current will be produced but the current in the secondary does not depend on the voltage,, it depends the load,, if load is not connected there will be no current at the secondary side  

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