In primary side of transformer it change magnet north to south as ac current flow and it keep changing as ac wave passed through coil. I do not understand why on secondary side we got a current which flow in one direction. Why not on secondary side current change its direction as magnet change in primary side.

  • 1
    \$\begingroup\$ how are you determining that the current flows in only one direction in the secondary winding? \$\endgroup\$
    – jsotola
    Commented Aug 31, 2020 at 22:39
  • 3
    \$\begingroup\$ It doesn't. It's AC too. Perhaps you are thinking about the output of a rectifier (which often follows a transformer)? \$\endgroup\$
    – user16324
    Commented Aug 31, 2020 at 22:50
  • \$\begingroup\$ Probably referring to a switchmode flyback power transformer, the power goes into the transformer as pulsed DC, and comes out as pulsed DC. \$\endgroup\$
    – BobT
    Commented Aug 31, 2020 at 23:11

1 Answer 1


The input and the output of a transformer are undoubtedly AC.

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You are most probably referring to a DC power supply which is a transformer plus a rectifier and a capacitor on the secondary side.

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  • \$\begingroup\$ Hi. I m talking about ac current. If current flow forward and back than how electric appliance works on it \$\endgroup\$
    – Garry
    Commented Sep 1, 2020 at 6:56
  • \$\begingroup\$ Hi Garry, The rectifier converts AC to DC which is unidirectional. \$\endgroup\$
    – vu2nan
    Commented Sep 1, 2020 at 8:07
  • \$\begingroup\$ Sorry I m not talking about DC. I want to know about ac only. \$\endgroup\$
    – Garry
    Commented Sep 1, 2020 at 10:36
  • \$\begingroup\$ I suppose you are referring to a wall wart transformer. In that case the rectifier would be in the equipment. \$\endgroup\$
    – vu2nan
    Commented Sep 1, 2020 at 13:45

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