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# A small doubt about Electrical Devices

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#### purifier

##### Full Member level 4
If an electrical device has constant power and frequency ( same power and frequency at input and output respectively ) then does it mean that the device is transformer ?

Is there no electrical device other than transformer which have constant power and frequency ( atleast one of them ) ?

If yes, then does it mean that conservation of energy is not maintained ( when I talk in terms of power ) ?

The philosophic approach to electronics will not give you useful and specific answers.
You must always have in mind that lossless devices simply does not exists.
Conservation of energy is always maintained.

I thought I got what you answered but it still gives me the same old doubts... Can you be a little more clearer please?

How many terminals does the device have? Are we talking about a two terminal device (like a resistor, capacitor, inductor) or a four terminal device (like a transformer).

The "ideal" transformer has no power loss as the input power equals output power. This is because the primary and secondary voltages and currents are natuarally scaled to give you the ratio. For example, a 2:1 transformer will have a half the voltage at the secondary (compared to the primary) but *twice* the current at the secondary (again compared the primary). In a real transformer there are losses, for example, the resistive losses in the copper wires that are used to construct the windings. Another thing about a textbook (ideal) transformer is that it passes all frequencies -- so the voltage and current transformation by the turns ratio is valid at all frequencies (even at dc). In reality, this is not true! The transformer will not pass dc and high frequencies (so it acts like a bandpass filter).

Cheers,
v_c

dear friend
take an example the transducers the transfer the power with same frequency from one shape ( electrical as example ) into other enegy shape with same power ( audio , light .... etc ) with same frequency but they donot mentioned as transformer

Also the idael DC-DC convertor tarnsfer same dc power from one lvel of voltage into other ( frquency=0 ) and they donot named transformers.

also if you think the ideal capacitors and coils does not dissipate power ( reactive power component only )and they maintain the frequency but they are not transformers

thankyou

You can call anything that converts something into something else a transformer!

And yes dc-dc converters are sometimes modeled and referred to as dc transformers. Take a look at any book on modeling of power converters - like Erickson's Fundamentals of Power Electronics!

v_c

don't confuse the frequency with constant power, b/c u might have read that:
I1/I2=V2/V1
so, ignore the freaquency...and then think of the contant power only...u will feel a bit ease of understanding ur problem...

Borber said:
The philosophic approach to electronics will not give you useful and specific answers.

In my opinion, electronics has always been philosopical on the cutting edge. The physics of the diode and the transistor were worked out on paper by logical deduction and imaginative conjecture long before they were created in a lab. Electronics fundamentals grow out of science. Science, to me is the marriage of conjecture and observation. I think the philosophic questions are the better ones.

When we talking about a device that has the same output power as the input power is then we can say the device is lossless. Under the term input we must consider all input sources like input signal power, DC supply power etc. The same is valid for the output. Term transformer can be used in many ways. We have voltage transformer, LED can be assumed as electrical to light power transformer etc. Is peace of wire a transformer? It is closest example of a device that has almost equal output power to input power. Can we call it a transformer?

It looks like purifier does not know what he wants.

purifier said:
If an electrical device has constant power and frequency ( same power and frequency at input and output respectively ) then does it mean that the device is transformer ?

Is there no electrical device other than transformer which have constant power and frequency ( atleast one of them ) ?

If yes, then does it mean that conservation of energy is not maintained ( when I talk in terms of power ) ?

all i can now tell is nowhere law of conservation is breached...

purifier said:
If an electrical device has constant power and frequency ( same power and frequency at input and output respectively ) then does it mean that the device is transformer ?

Yes, It may be a transfermer but i think it's not the only case for such device!

and that replies on your second question also,