How do extension cables affect electrical power?

Question

After looking into an extension cable, it seems that all of the sockets are connected in parallel; i have a few questions

1. Am i correct? (are they in parallel?)
2. Do extra devices affect current?
3. Do extra devices affect Voltage?
4. Can a house compensate for this change (if there is one)
5. If so, How do they do this?

All answers are appreciated, but please try to stick to the question.

Thank you
XD:

Answer 1

An extension cable has a socket on its user end that is wired exactly as the house socket is, straight through (not parallel). Thus the active, neutral and earth connections are identical in position to the house socket. That is important.

The wire gauge used in the extension determines the maximum current that can be used on the extension end, and also length needs to be considered.

That maximum current is usually specified by the manufacturer, and is the recommended current not only that you should draw from the extension, but allows for the inevitable voltage drop along the extension to be within an acceptable range for most purposes the extension might be used for.

All conductors have an ohmic resistance, the larger the wire diameter the less resistance, the more current the wire can carry without undue heating and voltage drop.

The longer the extension, the larger the diameter of conductors needed to carry high current and have acceptable voltage drop at that current.

No, the house cannot compensate for losses in an extension.

Yes, more operating devices need more current and voltage drop will be greater.

Yes, it is POSSIBLE to compensate by use of a voltage transformer, but it is far more cost effective to have an extension with thicker conductors. In addition, if current beyond manufacturers' recommendations were used from an extension lead if you DID compensate, it will overheat, which makes the problem more severe, plus risk of fire.

Answer 2

1. All sockets are in parallel, yes.

2. The currents drawn by all devices are added together and drawn from the house. So if you have 2 devices drawing 3 and 7 amps respectively, the extension cord (cable) will draw 10 amps from the wall.

3. Any time current is drawn, there is a small voltage drop. The voltage drop is generally insignificant to the device plugged in. For example, if your line voltage is 220, and a lot of things are plugged in, the line voltage may fall to 218 at a device. This is less than the line voltage would vary anyway, through the day.

4. To some extent, the house does compensate for the change.

5. The explanation involves transformers and current hogging. Without getting too technical, a house will have a transformer to connect it to the street. All these transformers are wired in parallel at the street. If your house has a significantly lower voltage than your neighbor's, your transformer will hog the current from the street until your voltage is approximately the same.

Answer 3

Yes and no. An alternating current is shared across multiple sockets. For example, if a fuse goes out or a circuit breaker switches, a number of power access points will go out depending on how it's wired. You don't really want to run everything in series because you can have a single point of failure. In modern day houses, you try to make that single point of failure happen at the fuse box or circuit breaker box.



1. In the house I live in, it's a mixture

2. Yes, if the microwave is on the oven light dims in this house. That means it's probably in series on a single fuse

3. If the current changes, so does the voltage (V = IR)

4. Sure

5. As long as there isn't a spike or a wave drop then normally there isn't a problem. The AC circuit is comprised of three out of phase waves in the US. If you drop one of them on the main power, chances are everything will go out.



But here is a good explanation... http://www.shopyourway.com/questions/1000761



The house I live in has both parallel and series wiring. It's an old house, so we have the occasional electrical problem.

Answer 4

roderick's answer is basically correct with one or two flaws.

3 - if the extension cord is long and the current being drawn is fairly high, the voltage drop is a lot more than "small". A really critical situation is with a circular saw which can be burned out by using it on too small and too long an extension cord - it uses a lot of current to start and doesn't drop its usage until up to normal speed - if it stays slow, it draws more current (for technical reasons) and gets hotter and hotter.

4 within the limits of the cord, the SYSTEM not the house compensates for the change - it tries to provide steady voltage all the way back to the generating station.