Slimming Down - my cords need to go on a diet like their owner!

[markis10]

Simplistically, Watts = Volts x Amperes ...

Thats power output, not power consumption which is I squared x R.

 

[serfty]

Thats power output, not power consumption which is I squared x R.

Simplistically it's the same thing.

In isolation: P = I²R = VI = V²/R

Now with application as distinct from theoretic the consumption would be generally considered more important; especially if you were looking to supply power to more more than one device.

FWIW, generally on the power pack one sees the output values for Volts and Amperes which tells us what the supply can produce, not what may be required by the attached device(s).

 

[NM]

Simplistically, Watts = Volts x Amperes ...

Well, that is "Apparent Power" and technically is measured in VA (Volt Amps) and not in Watts unless the Power Factor is exactly 1. If its a DC circuit, then Apparent Power = Real Power, but in an AC circuit, the Power Factor is rarely 1 so Apparent Power (measured Volts x Amps) will be greater than Real Power (V x A x PowerFactor, measured in Watts).

Thats power output, not power consumption which is I squared x R.

Simplistically it's the same thing.

In isolation: P = I²R = VI = V²/R

And should be noted with the units Volt Amps (VA). Is only when the load results in a Power Factor of 1 that Power in VA = Power in Watts. A Power Factor is 1 is achieved when the load is purely resistive. But in reality loads are likely to include a capacitive and an inductive component, especially when a transformer or any form of coil (e.g. a motor) is involved.

Now with application as distinct from theoretic the consumption would be generally considered more important; especially if you were looking to supply power to more more than one device.

FWIW, generally on the power pack one sees the output values for Volts and Amperes which tells us what the supply can produce, not what may be required by the attached device(s).

and its generally the power output that is quoted (i.e. x Volts at y Amps in the low-voltage/output side). This should reflect the maximum continuous power (measured in VA) that can be delivered to the load without over-heating or causing damage in any way.

Then again, in practical terms what you state is correct

 

[dfcatch]

Geebus!!

I should have paid more attention in physics

 

[SeatBackForward]

Fantastic...I'm learning things, see!

Ok so my Laptop power pack has Output of 19V at 3.42A, so a 70 Watt adapter would be sufficient?

 

[SeatBackForward]

Just to further add to this thread. I recently got myself one of these off Ebay too:

for recharging all them USB powered devices in a car. The adapter is tiny, barely sticks out of the cigarette socket itself.

 

[markis10]

Bought one of these last night for $9 delivered, I will be curious to see how it goes but it might solve a few issues. Also got one of these to reduce two cables into 1

 

[SeatBackForward]

View attachment 6282


Bought one of these last night for $9 delivered, I will be curious to see how it goes but it might solve a few issues. Also got one of these to reduce two cables into 1

View attachment 6283

The first one is the mock-Kensington adapter, that was also available on-board duty free a while ago too. I had one, but found that the weight of the adapter itself would drag it off the powerpoint occassionally, i ditched it for one of these:

and must say im much happier with it.

 

[dfcatch]

They're still available on-board duty free

 

[Daver6]

Quite handy having a multi-country adaptor in your carry on so you can use inflight power

 

[SeatBackForward]

Quite handy having a multi-country adaptor in your carry on so you can use inflight power

With the one I have above, it also doubles as a USB port too, to charge up the phone/tablet/camera/NC headphones/Portable Wifi router etc etc whilst using the laptop... Best little gadget i've bought for a while actually.

 

[ozscot]

SeatBackForward, what brand is that? Looks good. Can you use the power outlet and USB at the same time? Will it charge an iPad?

 

[markis10]

The one I got also has the USB, will be interesting to see how it goes.

 

[SeatBackForward]

SeatBackForward, what brand is that? Looks good. Can you use the power outlet and USB at the same time? Will it charge an iPad?

I got mine off Ebay, here's a link to the category that has them (and others): Link, cost about $24 all up including delivery.

Its not any brand as such, just that generic made in China sort, but often enough even the branded ones are the same thing. The USB output is only 500mA (Apple products need 1000mA) so it probably wont work with the Ipad, i dont own any apple products so can't confirm.. Let me checktonight when im back home what the output is as i've had no problems using it with my things.

 

[markis10]

I thought Ipads need 2A to rapid charge, they all still charge regardless, just slowly and only when they are not being used.

 

[SeatBackForward]

I thought Ipads need 2A to rapid charge, they all still charge regardless, just slowly and only when they are not being used.

I think that is the case, its more what they call a "trickle charge". I use the adapter to recharge my phone when I have my laptop packed away. Otherwise my laptop has a powered USB port that will still charge through the USB cable, even when the laptop is turned off - and I mainly use this one.

 

[SeatBackForward]

I'm considering getting one of these too soon, so that I can have my own power adapter rather than whatever my IT dept issues me with..