Why can't you transform DC?

Answer 1

we can't use dc everywhere because dc is hazardous for living beings plus we can't transform mechanical energy into dc power directly.

you can see that we use basically ac appliances at home,also dc but with very low voltages. ac is alternating in nature has zero and negative so if any one get in contact with ac it will result in hazard for the half positive cycle and repelling of body for the negative cycle. but in case of dc, the supply is continuous so it'll hazard the body continuously.

another aspect is generation. as i told earlier that we can't transform mechanical energy into dc power directly means we are generating ac supply in most generating stations where we are dealing with mechanical energy conversion. even dc generator generates ac power but by means of commutation process we convert it into the dc.

so it is not possible to use dc or ac everywhere. we have to deal with the both :)

Answer 2

Transformer work on principle of electromagnetic induction. If flux generated in primary winding is continuously changing and it is also linking with secondary winding then voltage will be induced in secondary winding. In AC supply, the instantaneous value of supply is continuously changing to follow sin wave at supply frequency ( increase from zero to maximum value, then reduce to zero then to negative maximum and then back to zero in every cycle) . This create continuously changing flux in primary winding which link with secondary winding of transformer, thereby inducing voltage in it. However in DC, the instantaneous value of supply voltage remain constant, no changes at all. Thus it cannot produce continuously changing flux and hence cannot induce any voltage in secondary winding. Hence DC cannot be transformed.

Answer 3

Transformers depend on fluctuating magnetic fields in order to operate. The operating principle of an inductor, of which a transformer is an example, is to resist a change in current by back EMF which bucks the change (up or down) in current. If you place DC across an inductor, the current would linearly increase until the resistive limit is reached, the power supply's capacity is reached, and/or the inductor self destructs from overcurrent.

Answer 4

Transformers operate on the principle of changing or fluctuating magnetic fields interacting with windings. If you used DC, there would be no fluctuation, and thus no useful output. Worse, since a transformer is an inductor, if you apply DC to it, the current would increase continuously, up to the point where an overload exists, possibly destroying the transformer or, at best, blowing the protective device.

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It is the alternations of the AC voltage that product the rising and collapsing magnetic fields around the wire coils. This magnet flux in the primary windings is what cut the coils of the secondary winding coils. This induced current of the secondary windings is what can be manipulated by the amount of windings in the secondary to produce either a step up or down transformer. Using DC you would induce a current in the secondary when the transformer was turned on as the inrush current flux cut the secondary windings and it would happen again when you turned the DC off and the magnetic field collapses. If you turned the transformer off and on at 50 or 60 times a second with a DC source you would get an output on the secondary side.

Answer 5

By definition direct current does not have alterations of current except when switched on (current rise) and when switched off (current fall). A transformer needs continuous rise and fall of current to induce a current into the secondary windings.