If two bulbs of wattage $25$ and $100$ respectively each rated at $220\, volt$ are connected in series with the supply of $440\, volt$, then which bulbs will fuse
Diffcult
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(b) Resistance of $25\, W$ bulb $ = \frac{{220 \times 220}}{{25}} = 1936\,\Omega $
Its safe current $ = \frac{{220}}{{1936}} = 0.11\,\,amp.$
Resistance of $100\, W$ bulb $ = \frac{{220 \times 220}}{{100}} = 484\,\Omega $
Its safe current $ = \frac{{220}}{{484}} = 0.48\,\,amp.$
When connected in series to $440\, V$ supply, then the current $I = \frac{{440}}{{(1936 + 484)}} = 0.18\,amp.$
Thus current is greater for $25\, W$ bulb, so it will fuse.
Its safe current $ = \frac{{220}}{{1936}} = 0.11\,\,amp.$
Resistance of $100\, W$ bulb $ = \frac{{220 \times 220}}{{100}} = 484\,\Omega $
Its safe current $ = \frac{{220}}{{484}} = 0.48\,\,amp.$
When connected in series to $440\, V$ supply, then the current $I = \frac{{440}}{{(1936 + 484)}} = 0.18\,amp.$
Thus current is greater for $25\, W$ bulb, so it will fuse.
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