does a transformer have to have a magnetic flux in it's core to transfer power or is it possible with say a 100% efficient transformer that it would not need to have any flux in it's core to transfer power, like say it had 1000watts on the primary and 1000 watts on the secondary(would that be possible with no flux in the core). any info would really help

 

flux changing is necessary for a transformer principle to work.
flux does not eat up energy, its the heat generated in the core due to hysteresis and eddy currents that account for the losses in transformer.
again there are also heat losses in the windings due to resistance of the windings.
did that help.

edit: so flux is absolutely necessary for working of transformer and is totally innocent( it does not account for losses its the other parameters of the transformer which are responsible and can be improved upon though it is not practically possible to reduce the losses to zero---BTW transformers have very high efficiencies often nearing 99%)

 

mr. recca is dead on. a primary could inductively couple to a secondary through air only, however, air is not very acceptant to flux so it would have poor efficiency. the use of a permeable core (usually silicon steel) greatly increases the coupling efficiency from primary to secondary.

 

mr. recca is dead on. a primary could inductively couple to a secondary through air only, however, air is not very acceptant to flux so it would have poor efficiency. the use of a permeable core (usually silicon steel) greatly increases the coupling efficiency from primary to secondary.

To clarify, magnetic flux exists in an air-core transformer (if an AC signal is applied).

 

thanks that really helped alot