Question 337: Current Electricity

Question

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
$$I = {{440} \over {{{\mathop{m R}
olimits} _{eff}}}},\,\,{{\mathop{m R}
olimits} _{eff}} = {R_1} + {R_2}$$
$${R_1} = {{V_1^2} \over {{P_1}}} = {{{{\left( {220} ight)}^2}} \over {25}};\,\,\,$$
$${R_2} = {{V_2^2} \over P} = {{{{\left( {220} ight)}^2}} \over {100}}$$
$$I = {{440} \over {{{{{\left( {220} ight)}^2}} \over {25}} + {{{{\left( {220} ight)}^2}} \over {100}}}}$$
$$ = {{440} \over {{{\left( {220} ight)}^2}\left[ {{1 \over {25}} + {1 \over {100}}} ight]}}$$
$$I = {{40} \over {220}}\,\,Amp$$
as $${I_1}\left( { = {{25} \over {220}}A} ight) < I\left( { = {{40} \over {220}}A} ight) < {I_2}\left( { = {{100} \over {200}}A} ight)$$
Thus the bulb marked $$25W$$-$$220$$ will fuse.

Answer

Both

Answer

$$100$$ $$W$$

Answer

$$25$$ $$W$$

Answer

Neither

Current Electricity

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?

Choose the correct answer: