it is clear that volts equal to the current as per ohms law.
is it appliable to the AC power or only for DC. if it is
appliacable to AC in transformers when voltage increases
the voltage decreases ????? why??????????????
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Answer Posted / 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.
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