You buy a 75-w lightbulb in europe. where electricity is delivered to homes at 240 v.

You buy a 75-W lightbulb in Europe,where electricity is deliveredto
home at 240 V. If you use the lightbulb in the United States at120
V (assume its resistance does not change). how bright will itbe
relative to 75-W 120-V Bulbs? [ Hint: assume roughly thatbrightness
is proportional to power consumed]

please show work.


resistance of bulb is found by:
    P = V2
/R          75
/R            R
= 768 ohms
Now find the power it uses when plugged into 120 V:
    P = V2 / R = 1202 /
768 =    18.75 Watts
So compared to a 75 watt bulb is it is only:
     18.75 /
75  =        1/4    
as bright

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Posts