i just obtained a transformer from a small ac-dc converter. usually, it converts the 240v ac (let's call it terminals a and c) to 4.5v dc (terminals d and c).what if i connect a 4.5 dc supply to the terminals d and c? meaning that where i would usually obtain the converted electricty, instead, i connect a 4.5 to it, leaving the terminals where i would usually connect to the wall empty. wouldn't the magnetic field step up to 240v?
TRANSFORMER BECOMES SMOKING IN A FEW SECONDS IF THE 4.5V DC HAS HIGH ENOUGH CURRENT.
You'll only get a voltage at the 240V terminals as you make and break the 4.5V connection. Enough to feel a zap if you were touching them. As others have said transformers are AC devices.
Short answer, NO. Your power converter is not a reciprocal device. While a transformer is part of the circuitry, it is most likely a switching converter. If you're talking about the transformer only, then you need to feed an AC signal in to it. Feeding 4.5VDC in to the transformer will short out your 4.5VDC supply, or cause it to supply lots of current which will be converted to heat.
Nope. Not at all. (Note: this only applies to transformers, not to modern DC-DC switch-mode converters that are used in power bricks and cell-phone chargers -- those usually won't work in reverse either, but that's another story) Transformers only work for AC. When you put DC into a transformer, you get nothing out on the other end. Assuming your converter uses a transformer, it probably consists of the transformer and a diode rectifier. If you try to put DC through the rectifier in reverse, it will block it. If you rip out the rectifier and put DC through the transformer, it will get very hot, but you won't get any voltage out on the other end. The reason transformers only take AC is that you need a a changing current to create a changing magnetic field to induce a current in the secondary winding. No change no induction.
