Why Does DC Lose Power Over Distance, and Why Is AC Used for High Power and 400Hz Systems?

Hi i am trying to understand basics of electricity please help me with following questions
Why DC losses its power when transmitted over long distances??,
Why all the high power devices uses AC than DC ???,
Why we see that frequency of AC 400 Hz is preffered???,
How a 28 volts or 26volts or any DC power source (battery) can produce 115 or 200 volts AC???,

Why DC losses its power when transmitted over long distances??,

Doesn't make sense, the question as asked.

Why all the high power devices uses AC than DC ???

A little research on your part is all that's required to answer this question

Why we see that frequency of AC 400 Hz is preffered???

When size and weight (aircraft example) are a factor and long distance transmission is not in the design, 400Hz is the answer otherwise 60/50 Hz is preferred.

How a 28 volts or 26volts or any DC power source (battery) can produce 115 or 200 volts AC???,

It's called an inverter and with solar panels everywhere it is hard to imagine you couldn't answer this.

Perhaps you are the ,"AMPLIFIER," person that stirred up a lot of trouble.

for the first question i want to ask that how DC will loose power if transmitted over long distance????

For 2nd please can u tell me any website or a clue why AC preffered for high power devices i tried but was unable to find out???

For third can you please tell me the affect of frequency difference on output
Means if i am operating a device on 115 volts 400 Hz AC & then i operate it on 115volts 50/60Hz AC what will be the affect on my device or any equipment.

One more question as we know for precision outputs of radars,radios we prefer DC continuous output,so why not we keep it the same way to use this DC for other equipments then to convert DC to AC then use it for operating

* Actually DC does not "lose power" over long distances any more or less than AC (speaking simplistically as there are other factors involving frequency). The reason AC is used for long distance transmission of power is that it can easily be "stepped up" (i.e. to a higher voltage using a transformer). At a higher voltage there is less current (P = IE). Less current means less power loss (P = I²R) -- 'R' being the resistance of the transmission line.
* Because AC can easily be converted using a transformer.
* Because of the tradeoff between higher freq = less iron, and the audio noise factor of higher freq (and ease of filtering) and long distance transmission as Earl said.
* Look up "inverter" -- i.e. it's achieved with complex circuity (not a trivial subject).

Why not tell us what you think the answer is to each question ?

Also, I'd imagine that the teacher would prefer you do your own homework.

for your first 2 question i think this link might help:
http://electroniccircuitdesignsharing.blogspo...12/07/why-transfer-power-at-high-voltage.html

all the best!

There is a project supplying a former PGE generating plant that was taken offline in SSF with an alternate power supply via a submerged conductor from an upstream power plant and it is carrying dc power. The times they are a changing. New Siemens technology from what I understand. I don't have all the particulars but my jaw hit the floor just like I am sure many of yours will, and Siemens too when they are besieged for info. A collegue and long time friend worked on the rectification building intercoolers. It is real.
I just don't see how the primary/secondary step up/down ability of alternating current can be beat by dc. It is a lot easier to send 1 amp at 100,000, 250,000, or 500,000 volts and then turn it back around on the other end and exagerating here for simplicity and not wanting to get up and get the calculator (before noon Sunday) for 100.000 amps at 1 volt, etc, etc, Even our residential suburban neighborhoods usually are supplied with at least 4160 volts. Then transformed down one last time by smaller transformers supplying approximately 1 block at a time. The dc supply mentioned probably is feasible due to the cooling advantage upon the conductor being submerged in 55 or so degree water. Abundant cooling.
Imagine the size of conductors required to carry power to a city without transformer advantage. Even when accounting for the skin effect and corresponding cable construction they would still be virtual tree trunks on poles. Maybe, and this is sci fi futeristic beyond our current laws of physics, but just maybe one day Tesla's far fetched transmission experiments will bear fruit as technology advances. Probably not in my lifetime, but you never know. Wasn't too long ago the only thing flying was bugs, birds, and squirrels.(before you say it, I included bats with birds not squirrels.
Wait, what if?????????????????

This reminds me of a power converter station that I toured, once, about 3 decades ago. If it still exists, it's in Sylmar, CA USA. It converts 500kV DC power sent down from Oregon to AC with giant mercury arc rectifier tubes (as tall as a two story house, if memory serves).

In fact, here it is on Wikipedia:

http://en.wikipedia.org/wiki/Sylmar_Converter_Station

No, this is not that installation.