Three light bulbs, a 100W, a 60W, and a 40W are attached in series as. Which light bulb will be the brightest.

Yellow: 100 W                                     

Pink: 60 W

Green: 40 W                                        

Blue: They will all be the same brightness

Purple: None of these.

Answer: Green: They all have the same current through them by Kirchoff 1. Therefore, which ever bulb has the highest resistance has the largest I^2R. The 40W bulb has the highest resistance because R=(120V)^2/Power.