Answer:
The European bulb would be (1/4) less bright than the standard 75 W US bulbs.
Step-by-step explanation:
The brightness of the bulb depends upon the power consumed by the bulb.
Electric power consumed in Europe = 75 W
But to calculate the power the same bulb would consume in the US,
Electric Power = IV
where I = current and V = voltage
From Ohm's law, V = IR; I = (V/R)
Electric power can be rewritten as
P = IV = (V/R) V = (V²/R)
So, we can obtain the resistance of the light bulb as it is used in Europe (whose voltage rating is 240 V) from this relation.
75 = (240²/R)
R = (240²/75)
R = 768 Ω
In the US, voltage rating is 120 V, for the European bulb,
P = (V²/R) = (120²/768) = 18.75 W
The power consumed by the European bulb in the US = 18.75 W.
Compared to the 75 W US bulbs, 18.75 = (75/4)
Therefore,
P(European) = P(US)/4
The European bulb would be (1/4) less bright than the standard 75 W US bulbs.