Ac V Dc

[Bazile]

I was listening to Womens hour ( i think ) earlier and one of the guests was talking about one of her ancestors who argued for AC as opposed to DC to be adopted for distribution .
I think she said that he said it was because it would benefit the poor rather than DC current .

Was that true and if so - how ?

[beso]

There are several technical advantages of AC over DC.

AC arcs are self-extinguishing making for easy switching and overload protection. If DC lines were allowed to touch the arc would not stop when the wires were separated.

DC can cause electrolytic corrosion of its own conductors.

AC has the simplicity of the transformer which converts voltages up and down, allowing very long distance transmission.

Large AC motors are far simpler than DC.

[Peter Pedant]

.

and Beso you have omitted the one we were taught at skool -
AC power transmission loss is less than DC

actually altho I thought - oh woman's hour !
the lady could be right .....
who was the power generator in America - Conn Edison ?
He apparently was very keen on DC transmission as his takings would rise in comparison [ and so therefore the poor would get less for their buck ]

[beso]

PP //and Beso you have omitted the one we were taught at skool -
AC power transmission loss is less than DC //

I am afraid they taught you incorrectly.


The efficiency associated with AC transmission is entirely due to the ease with which it can be transformed to higher voltages and back down again. At higher voltage the same amount of power can be transmitted at a lower current, reducing the resistive losses in the wire.

DC is intrinsically more efficient than AC which is one reason why it is used for very long transmission lines.

AC induces an oscillating magnetic fields causing eddy currents to flow in any surrounding conductive materials. Indeed AC transmission is not suitable for undersea transmission more than a few kilometres because salt water is very conductive.

Power is also lost through capacitance between the wire and the ground.

At AC high voltages corona discharge also becomes an issue.

[Peter Pedant]

// I am afraid they taught you incorrectly. //

you are absolutely correct Beso - there were we having to integrate half sinusoidal waves [AC] and showing that it is clearly less than the rectangle surrounding it [DC] I2R and all that sort of crap - integral mean value theorem springs instantly to mind

and in War of the currents

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

they say exactly as you

I am shocked - I am deeply shocked