Does my computer slow down the Internet for other devices in the house?

I'm on Sky broadband and my PC is connected to it through an Ethernet cable. As well as my PC an ipad, 2 iphones and an Xbox are connected to it wireless. Will my PC being on affect the internet on the Xbox?

It depends what you're doing on your PC, but potentially yes, especially if you are watching a video, or downloading something, etc.

Imagine your internet connection is a small hole in the wall. You can only fit so much stuff through it at once. The more you try and squeeze through that tiny hole in the wall, the slower things become. This is called bandwidth.

Your modem will only allow a certain amount of data through in a certain time. The more things which are trying to get data at once, the less each of them will be able to get. I notice that my laptop takes much longer to download things if my daughter is home and has her laptop and smartphone on as well.

Yes it will be effected, As you see, The more devices you connect the speed will be slower and the network divides the speed to everyone as in equal bases, But remember if you arent using the internet on the other devices and just using on one device than the speed is yours fully, but if any other device is using the data then the speed gets dived for example updates, internet app message etc, Divides the speed too.

It depend on your internet speed. If you have 30mb or high then it is not your PC. Try connecting most of the device through the Ethernet cable if they are near to the router. To many device connected wireless could slow the internet down.