A light bulb uses 40.0 W of power when connected to a 110 V (DC) outlet. If the same bulb is connected to a European 220 V outlet, how much power will the bulb use?

Answer 1

Solution:

The power in watt P = I²R = (IR)I = VI where V is the voltage in Volts (V) and I is the intensity of the current in Amps(A)

Note That 1W = 1V . 1A , then the intensity of the current is I = P/V = 40 W / 110 V = 0.36 A

for a 220 Volts source outlet , the power in the bulb is P = VI = ( 220 V)(0.36 A) = 79.2 W