Thaqalain said:
I want to apply DC safely to the primary of a transformer,how can i
do?by
*When limiting resistance is in series.
*When limiting resistance is in parallel.
*when neither of above
The windings of a transformer act just as any other piece of wire
where DC is involved, so think of how you could safely connect wire
across a DC supply.
If the supply is a voltage source (voltage essentially constant, no
matter how much current is drawn from it), than adding other loads in
parallel with the wire would only provide additional paths for more
current, without limiting or reducing the current through the wire.
Resistances connected in series (the wire is just a low value
resistance) add. So a series resistor will reduce the current that
passes through the transformer winding.
If, however, the DC supply is a current source (which means that the
current is nearly constant, regardless of how much resistance is
connected across it because it varies its voltage to whatever is
necessary to drive that current), then paralleling the wire with other
resistances would detour some of that total current to other paths,
lowering the total voltage the supply needed to produce to maintain
the fixed, total current. This lowers the fraction of that total
passing through the transformer.
Since your mention of "applying DC" does not specify whether the
source is more like a voltage source or a current source, or something
in between, the question cannot be answered, except to discard the
third choice.
Tell your teacher that you learned this on the Internet, not in their
class.
