Question

three identical bulbs are connected in series across a source consume 20W power. of the bulbs are connected in parallel to the same source the power consumed is

Answer 1

we know that P=v^{2}/R

let a bulb be of resistance R

if in series then the equivalent resistance=3 R;

then P=v^{2}/3 R;

20 W=v^{2}/3 R;

60=v^{2}/R-----------------------------------------1

if in parallel then the equivalent resistance=R/3;

then P=3 v^{2}/R;

{since v^{2}/R=60 then}

P=3*60;

P=180 W;

therefore the power consumed is 180 W