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Answer 1 · 2015-10-15T16:12:22

60W lamp is brighter.

Suposing both lamps are designed to operate with the same voltage, as 220V:

The resistance of the 60W lamp is:

#R = v^2/P# = #220^2/60# = 806,67 Ohms

The resistance of the 250W lamp is:

#R = 220^2/250# = 193,6 Ohms

If we connect both in series at a 220V mains, the current will be:

I = #220/(806,67 +193,6)# = 0,22 A

As far as Power = #R*I^2#,

The power dissipated by the 60W lamp is:

P(60) = #806,67*0,22^2# = 39W

And the power dissipated by the 250W lamp is:

P(250) = #193,6*0,22^2# = 9,37W

So, the 60W lamp will be brighter.