# simple question regarding transformer

Discussion in 'General Electronics Chat' started by yourfriendahsan, Jul 20, 2008.

1. ### yourfriendahsan Thread Starter Member

Jul 5, 2008
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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.

2. ### pntrbl Active Member

Apr 21, 2008
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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 ...

SP

3. ### yourfriendahsan Thread Starter Member

Jul 5, 2008
11
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that means i have to use hard methods to step up dc?

4. ### Audioguru New Member

Dec 20, 2007
9,411
896
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.

May 16, 2005
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6. ### theamber Active Member

Jun 13, 2008
318
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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.
http://www.ehow.com/how_2252605_make-voltage-divider-circuit.html
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.
www.williamsonlabs.com