Confusion with new lights fitting

[Paul Ellis]

Hello,

I have fitted a double insulated light fitting in my bedroom with no problems.

I had lying around a voltage tester, now I understand these are very unreliable, but when I touch the fitting with it, it will light up. There's a few other appliances that it'll do the same.

I'd just like to know why this happens?

 

[Pete999]

Was it a pen type tester?

 

[Paul Ellis]

Yeah it was

 

[telectrix]

these detectors work on induced voltage. although useful as an indicator,they are about as reliable as an ashtray on a motorbike.

 

[Rosco]

Rub it on your jumper and see what happens

 

[dmxtothemax]

it is picking up the electro-magnetic field
from the fitting.