when 40 watts and 60 watts bulb is connected in series,
which bulb glows brightly ?

Answer Posted / syed golam kibria

'V' across both the bulbs will be the same...
we have,
P=V^2/R;
R=V^2/P;
so calculating resistances,
R60=240*240/60=960ohm,
R40=240*240/40=1440ohm,
Req=(960*1440)/(960+1440)=576ohm,
Total current through the circuit:
240/576=0.625A
current through the 40W bulb,
0.25A
current through the 60W bulb,
0.375A
Now,
E=i^2*r*t
E40=0.25*0.25*1440*t=90t
E60=0.375*0.375*960*t=135t
for a same time period 't'...60W bulb dissipates more energy...
so the 60W bulb glows brightly...

Is This Answer Correct ?    4 Yes 27 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

can i use the six sigma method which is used in management area, in state estimation of power systems?

1387


Why it is necessary to isolate fire fighting when you are taking shutdown for lv board.

1195


On what cycle does thermal power plant operate?

656


how can I calculate charging current of cable/overhead conductor? what is roll of voltage in it ?

3236


For a spring controlled governer the relation F = ar+b (F is the controlling force, r is the radius of rotation a and b are constants), indicates that the governer is

734






what can be the causes of capacitor start motor having a higher current that its actual

1514


defination of lines

1546


how mass curve differs from hydrograph.

1302


I want single line diagram for AMF & DG syncronizing panel

6632


What is the distance between body earthing and neutral earthing.?

4113


dear all i am kumara now current working in electrical designing of control and relay panel i want learn some substaion design then any book are available. pls mention name and authour

1516


Load transfer in 11kv double busbar switchgear - operation.

1507


what is the standard values(Megger test) of resistances between L&N,L&E and N&E for a system on IEE regulations?

1661


What is use of starter and choke in tube light

1304


can you any one give exact mathematical relation between AC current and DC current?

1403