An electric bulbis marked 250v - 200v.What information do markings convey? How many joules of energy is consumed by the bulb in one hour? How long will it take for the bulb to consume one kilowatt hour?

The bulb must be marked as  250W-200V. Both the markings are not in volt ,one defines the power and other the voltage at which the bulb operates.                                

Energy consumed in one hour =Power *time=250*60*60=900000J

to consume 1kWh=1000Wh=250*t

t=4 hours

It must be marked as 250W-200V.  The first is the power rating (the power that is consumed by the bulb) and the second is the voltage rating (the voltage at which the bulb operates.

energy consumed by the bulb =Power * time=250*60*60=900000 J

To consume 1kWh=1000Wh=Power*time=250*time

Time=4 hours