simple question regarding transformer

Thread Starter


Joined Jul 5, 2008
I am beginner in electronics last night i experimented to step up 12 volt dc

i took out a transformer from multimedia speakers of my pc. when i manually checked that transformer then i found that its purpose in the speakers was just to step down 220 vac to 12vdc, when i connected it to my 12 volt battery then it gave 0 voltage.

According to my knowledge ( i am 10th grade student) it should step up the voltage so, why it's not doin that?

plz reply soon i am very curious to know itz answer.

thx in advance


Joined Apr 21, 2008
Transformers only work with AC. They need magnetic flux lines from the primary to cross the secondary thereby inducing current. With DC you only got on the flux lines established once when you hooked it up. With AC they just keep cycling away back and forth which keeps exciting the secondary ...



Joined Dec 20, 2007
If you want to make a square-wave inverter then simply make a low frequency square-wave oscillator that drives some power transistors that drive the transformer.


Joined Jun 13, 2008
First you have to get something clear about the differences between AC and DC. They both use different methods to step up or down voltages.
In AC to AC the usual way is done with transformers to step UP or Down.
To fully understand transformers is not easy they also come with current and frequency ratings limits.
Usually if you apply DC to a transformer it will just produce heat.
In a DC to DC configuration the usual way is with a "Voltage divider network" (resistors in series) to step it Down only because resistors are pasive devices.
A "DC to DC voltage converter" is used to step either Down or Up.
If you want to mix AC and DC in the process then it gets more complicated.
This is an online tutorial on electronics with plenty of animations.