Current Electricity Charging Discharging Of Capacitors Question 547
Question: What will happen when a 40 watt, 220 volt lamp and 100 watt, 220 volt lamp are connected in series across 40 volt supply
[BHU 2004]
Options:
A) 100 watt lamp will fuse
B) 40 watt lamp will fuse
C) Both lamps will fuse
D) Neither lamp will fuse
Show Answer
Answer:
Correct Answer: D
Solution:
Bulb (I) : Rated current $ I _{1}=\frac{P}{V}=\frac{40}{220}=\frac{2}{11}amp. $ Resistance $ R _{1}=\frac{V^{2}}{P}=\frac{{{(220)}^{2}}}{40}=1210,\Omega $ Bulb (II) : Rated current $ I _{2}=\frac{100}{220}=\frac{5}{11}amp $ Resistance $ R _{2}=\frac{{{(220)}^{2}}}{100}=484,\Omega $ When both are connected in series across 40 V supply Total current through supply $ I=\frac{40}{P _{1}+P _{2}}=\frac{40}{1210+484}=\frac{40}{1254}=0.03A $ This current is less than the rated current of each bulb. So neither bulb will fuse. Short Trick : Since VApplied < VRated, neither bulb will fuse.
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