An electric bulb is marked $200$ V, $100$ W. Calculate electrical resistance of its filament. If five such bulbs are connected in series to a $200$ V supply, how much current will flow through them?

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Solution

Rating of bulb is given as $220 V, 100 W$ i.e $V_{b} = 200 V$ and $P_{b} = 100 W$
Thus resistance of bulb $R = \frac{V_{b}^{2}}{P_{b}} = \frac{(200)^{2}}{100} = 400 Ω$
Equivalent resistance of $5$ bulbs connected in series $R_{s} = 5 R = 5 \times 400 = 2000 Ω$
Supply voltage $V_{s} = 200 V$
So, current in the circuit $I = \frac{V_{s}}{R_{s}} = \frac{200}{2000} = 0.1 A$

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An electric bulb is marked 200V, 100W. Calculate electrical resistance of its filament. If five such bulbs are connected in series to a 200V supply, how much current will flow through them?

Rating of bulb is given as 220 V,100W i.e Vb=200 V and Pb=100 WThus resistance of bulb R=V2bPb=(200)2100=400 ΩEquivalent resistance of 5 bulbs connected in series Rs=5R=5×400=2000ΩSupply voltage Vs=200 VSo, current in the circuit I=VsRs=2002000=0.1 A

An electric bulb is marked $200$ V, $100$ W. Calculate electrical resistance of its filament. If five such bulbs are connected in series to a $200$ V supply, how much current will flow through them?