Since the secondary winding has twice as many turns as the primary winding, the voltage induced in the secondary will be double the voltage that you apply to the primary.
If you connect a source of 200 volts to the primary, then you will measure 400 volts across the secondary. (Note: Please work with AC only. If you apply DC to a transformer, the output consists entirely of smoke.)
Power = (voltage) x (current)
If a floodlight across that secondary winding draws 5 Amperes, then the power dissipated by the light is
Power = (400 v) x (5 A)
Power = (2,000) VA
Power = 2,000 watts
Power = 2 kilowatts