Hello everyone, just don't understand -
/vol_2/chpt_9/1.html - here it is written, that "...an alternating current forming in the primary coil -- 180o out of phase with the secondary coil's current "
but here:
/vol_2/chpt_9/4.html - it is written, that "...Primary and secondary currents are in-phase. Secondary current is stepped up by a factor of ten."

So I am very confused - are they in phase, or out of phase?
Help please!!

 

Read this chapter again
http://www.allaboutcircuits.com/vol_2/chpt_9/4.html

 

Still confused. Current through R2 is in phase with Voltage on L2, so it means, that MMF induced by L2 must be +90 degrees to L1 MMF. If so, how these two MMF (L1 and L2) may work against each other?

 

Both the statement are true
"...an alternating current forming in the primary coil -- 180o out of phase with the secondary coil's current "

here its saying that the primary coil's current is 180 deg out of phase with with the secondary coil's current , the current flowing through the coil .

Now

"...Primary and secondary currents are in-phase. Secondary current is stepped up by a factor of ten."

Now here its saying that the current applied to primary coil from AC source is in phase with the current exciting or getting out from the secondary coil to some load connected with the secondary coil i.e.. the AC source current and the current flowing through the load connected with the secondary will be in phase.

Hope that clears a bit and read once more the chapter.

Good Luck

 

Understood. Thank you!!!

 

No ,the secondary coil is behaving as a source to the load so it is giving out current like a battery gives out a current.No current is entering in secondary coil only current is exciting from it.The current is generated by the secondary coil because of the changing magnetic flux in the core.In simple way think secondary coil as a power source.