Lamp dims ever so slightly when electric kettle switches on

[AMAC47]

I have just moved into a flat built in the late 70s. I am in the process of refitting the kitchen and have a temporary lamp in the kitchen plugged into standard 13 amp socket. Have noticed that when the electric kettle is switched on the lamp dims a little and then brightens slightly when kettle goes off. Have also noticed this effect in other rooms when electric heater or the like is switching on/off. Any ideas! Lamp is in a separate socket but is on the ring circuit.

 

[breezer]

its when the kettle comes on when you turn the light off you have to worry about.

serioulsly its voltage drop, its quite common.

 

[Steve]

It amazes me that people get to adulthood and still have never noticed this sort of thing. Electric showers, kettles, toasters, most heating appliances make lights go slightly dim.

 

[breezer]

its probably as a kid you are not allowed to use said items, mind you our kettle was gas, my mum still uses one, wont have an electric kettle, or toaster come to think of it

 

[AMAC47]

Yes, thought it was voltage drop but have never experienced it in the other houses I have lived in and though it might be due to old wiring or corroded connections.

 

[breezer]

becaaue you are now in a flat chances are other flats are on same phase as you, also with a table lamp its more noticeable.

you could always get an energy saving lamp. from new they are dim and get brighter

 

[mapj1]

The severity of voltage drop depends on the resistance between the substation transformer and the point in your wiring where lighting and power splits - normally fixed lights are on a separate circuit so this point is at the consumer unit. A plug-in light experinces the full drop of the final circuit cables too, so is more noticably affected, particulary if the distance ot the consumer unit is long.
If you are a long way from the sunbstation, the companies supply impedance may be a good fraction of an ohm (maybe more than half an ohm in some cases... 30A supply, long rural feed etc.) so a 13A kettle might drop 7V, a dimming effect enough to be seen. Of course if your old house was next door to the subst, then the resitance could as well have been <0.1 ohm, so dimming not noticable. In any case, not sinister unless it suddent goes from not noticable, to really bad, in which case something is going high reistance, which can be an early warning of a failure.