QJEEM12Ph579f: JEE Main 2012 Physics - Class 12 JEEM12Ph579f Solution: Two electric bulbs marked and are connected in series to a…

Question

Verified Solution • 2025–26 Session moderate

Two electric bulbs marked

25W

-

220

V

and

100W

-

220V

are connected in series to a

440

V

supply. Which of the bulbs will fuse?

Accepted Answer

The current upto which bulb of marked

25W

-

220V,

will

not fuse

{I_1} = {{{W_1}} \over {{V_1}}} = {{25} \over {220}}Amp

Similarly,

{I_2} = {{{W_2}} \over {{V_2}}} = {{100} \over {220}}\,Amp

The current flowing through the circuit

AIEEE 2012 Physics - Current Electricity Question 307 English Explanation

I = {{440} \over {{{\mathop{\rm R}\nolimits} _{eff}}}},\,\,{{\mathop{\rm R}\nolimits} _{eff}} = {R_1} + {R_2}

{R_1} = {{V_1^2} \over {{P_1}}} = {{{{\left( {220} \right)}^2}} \over {25}};\,\,\,

{R_2} = {{V_2^2} \over P} = {{{{\left( {220} \right)}^2}} \over {100}}

I = {{440} \over {{{{{\left( {220} \right)}^2}} \over {25}} + {{{{\left( {220} \right)}^2}} \over {100}}}}

= {{440} \over {{{\left( {220} \right)}^2}\left[ {{1 \over {25}} + {1 \over {100}}} \right]}}

I = {{40} \over {220}}\,\,Amp

as

{I_1}\left( { = {{25} \over {220}}A} \right) &lt; I\left( { = {{40} \over {220}}A} \right) &lt; {I_2}\left( { = {{100} \over {200}}A} \right)

Thus the bulb marked

25W

-

220

will fuse.

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