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# Help me understand! Two electric bulbs marked 25 W-220 V and 100 W - 220 V are connected in series to a 440 V supply .Which of the bulbs will fuse?

Two electric bulbs marked  25 W-220 V and 100 W - 220 V are connected in series to a 440 V supply .Which of the bulbs will fuse?

• Option 1)

both

• Option 2)

100W

• Option 3)

25 W

• Option 4)

neither

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N

As discussed in:

Series Grouping -

Potential - Different

Current - Same

- wherein

$I_{1}=\frac{P_{1}}{V_{1}}$

$I_{1}=\frac{25}{220}Amp$

Similarly,

$I_{2}=\frac{P_{2}}{V_{2}}=\frac{100}{220}Amp$

The current flowing through the circuit $I=\frac{440}{Reff}$

$Reff= R_{1}+R_{2}$

$R_{1}= \frac{V^{2}_{1}}{P_{1}}=\frac{(220)^{2}}{25}$

$R_{2}= \frac{V^{2}_{2}}{P_{1}}=\frac{(220)^{2}}{100}$

$\therefore I=\frac{440}{\frac{(220)^{2}}{25}+\frac{(220)^{2}}{100}}$

After solving this, we get $I=\frac{40}{220}Amp$

$\because I_{1}(=\frac{25}{220}A)< I(=\frac{40}{220}A)

Thus the bulb rated 25W-220V will fuse.

Option 1)

both

Option 2)

100W

Option 3)

25 W

Option 4)

neither

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