Sorry I'm a total newbie, hope this is in the right place.
I have a circuit with a 10v bulb and a standard 9v battery, but as such things as this exist:

http://www.ebay.co.uk/itm/OnSolar-3...SBC-and-E14-fittings-12v-to-24v-/261089907829

Could I just use this instead and everything be ok?
many thanks for any help anyone can offer.

 

My guess, and it's just a guess, is no. A standard 9V doesn't can't provide enough current to maintain that voltage, and it will soon sag below 8V.

I assume whoever wrote that the bulb would work at 10V was being as generous as possible. If they could have said 9V or 8V, they would have.