As per the literature I have gone through about voltage, current, impedance, magnetic flux, etc what I understand is that, at the secondary side of a step up transformer, the voltage is very high and the current is little to not at all. When I read this I visualise that in the secondary coil of a step up transformer, all the atomic dipoles (consisting of free electrons at one side and holes at other side) orient in one direction, so at the terminals the resultant electric field aka voltage is very high, however when electrons try to move towards the positive side under the influence of strong electric field or high voltage, electrons find it very difficult to move because of impedance which is majorly caused by ohmic resistance of long wire and inductive reactance of magnetic flux created by the secondary coil aka back MMF, or caused back EMF induced flux), is my visualisation correct so far?

And just like magnetic field appears when all the magnetic dipoles align themselves in same direction, I visualise electric field when all the charges orient themselves in one direction so all electrons point towards negative terminal and all holes point towards positive terminal, is my visualisation correct about electric field?

If my understanding above is not correct, please educate me as what exactly happens at microscopic level in the secondary coil so voltage or electric field becomes higher and current becomes lower or not at all.

I pardon if my query is dump, I am trying to understand the physics behind the phenomenon. I know it's a physics question, but since I didn't find any answers there so I am posting it here.

Thanks all!

  • 1
    \$\begingroup\$ Electrons and holes don't have an orientation. They have to move to move for current to flow. \$\endgroup\$
    – Finbarr
    Commented Oct 27, 2022 at 8:32
  • \$\begingroup\$ If you want to somewhat visualize a high AC voltage with no current you might think of an ocean wave hitting a solid seawall, (the wavy voltage is there but there is no flow). As for electrical charges, they do not orient themselves, they may collect at one position or another. When there are more of electrons than normal that would be known as a negatively charged area. A higher then normal collection of (so called) holes would be a positively charged area. Opposite charges attract each other while similar charges repel each other. An electric field will exist between opposite charges. \$\endgroup\$
    – Nedd
    Commented Oct 27, 2022 at 9:12
  • \$\begingroup\$ The ohmic resistance of the wire isn't the main reason the current is lower. It will still be lower, even if you use a bigger core for the transformer and use the space to wind the secondary using thicker wire. And if the current in the secondary is zero, it's because you haven't connected anything to it yet. \$\endgroup\$
    – Simon B
    Commented Oct 27, 2022 at 10:00
  • \$\begingroup\$ "all the atomic dipoles" Is this more suited for Physics.SE? \$\endgroup\$
    – winny
    Commented Oct 27, 2022 at 10:09
  • \$\begingroup\$ Here is more info on the operation of a step-up transformer: linquip.com/blog/what-is-step-up-transformer \$\endgroup\$
    – Nedd
    Commented Oct 27, 2022 at 11:08

1 Answer 1


How to visualise high voltage and no current at secondary side of step up transformer?

Ideal transformers (simplistic explanation)

  • Transformer primary and secondary coils share a common magnetic field
  • The magnetic field is produced by the magnetization current flow in the primary
  • This is due to the applied voltage and the primary inductance
  • The magnetic field magnitude is proportional to the applied voltage
  • Due to induction laws, the induced voltage in the secondary is proportional to turns and the magnetic field amplitude
  • Due to induction laws, the magnetic field generated by the primary is proportional to turns and the applied voltage
  • In an ideal transformer (100% coupled magnetic field), the ratio of the output voltage to the input voltage is directly related to the ratio of secondary to primary turns

Grasp this first then move onto non-ideal transformers


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