A 100 watt lamp glows brighter than a 25 watt lamp. What do you know about the resistences of these two lamps. How can you increase their power.
P = V^2/R
Assuming that the voltage V is the same for both lamps, the lower-R lamp bulb uses more power, and produces more light.
Power can be increased somewhat by inccreasing V, but this will greatly shorten the life of the bulb. A 20% increase in V may burn it out right away.