So,if i can show you an EMF being produced across a coil,where there is no magnetic field present,would you rethink your belief about a changing magnetic field being the producer of the electric field?
Depends on the exhibition. If you just show the transient situation where the magnetic field is zero (but actually passing through zero) while the coil produces a voltage I would not be impressed. If you can show emf being produced over a period of time while there is zero magnetic field over that period of time then I would be prepared to rethink things.
The electric field exist around a coil before current flows through it,and the magnetic field onlly exist once current starts to flow.
Would you like to expand on that statement as it doesn't make sense to me? What have you observed to lead you to that belief?
Will an EMF on my secondary (in my DUT) be in phase with the voltage across my primary,or will it be in phase with the current flowing through my primary?.
The answer depends on the conditions. Firstly I assume that you have a low impedance voltage source driving the transformer (for current driven transformers the answers would be different). Secondly I assume that you have a good transformer with tight coupling between primary and secondary so that leakage flux is negligible.
(a). If the secondary is open circuit the only current flowing is the primary magnetizing current that is 90 degree phase shifted from the primary voltage. The secondary voltage is in-phase with the primary voltage, so it is 90 degree shifted from the primary current. The magnetic flux is of course related to that magnetizing current.
(b). Now apply a light load and we get secondary current, we also get primary
load-current that is in phase with its voltage. Primary
magnetizing-current remains 90 degree shifted from its voltage, so the two quadrature components of current (
magnetizing plus
load) form a vector that is less than 90 degree shifted from voltage. Magnetizing-current and its consequent magnetic flux remain at their previous values. Secondary voltage remains in phase with primary voltage, but is now at less than 90 degrees shifted from primary current.
(c). Moving to a heavy load that draws primary load-current much greater than magnetizing-current we end up with primary current almost in phase with primary voltage. The secondary voltage is still in phase with primary voltage but now also almost in phase with primary current. The (now relatively small) magnetizing-current and its consequent magnetic flux remain at their previous values.
(d). If you take this further to a very heavy load that is almost a short circuit you get to a situation where the system is unable so sustain the same value of flux, currents are so high that primary and secondary resistance cause voltage drops that affect what you are measuring so I can't give a definitive answer.
What some people find hard to believe is that the high values of primary and secondary load currents that are in-phase with the voltages do not themselves produce any magnetic flux. (They do in a poor transformer where they drive leakage flux). The two load currents flow in opposite directions around the core and have a cancelling effect. That begs the question, if the secondary current does not produce any magnetic field how does the primary know that the secondary is there? The answer is that the secondary produces a mmf (ampere-turns) and the transformer has the ability to always match up the primary load-current mmf to that value. It acts something like a balanced bridge in that respect.
Smudge