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Question
An electrical bulb is marked 200V, 100W. Calculate the electrical resistance of its filament. If five such
bulbs are connected in series to a 200V supply, how much current will flow through them?
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Solution
Voltage V = 200 V, Power P = 100 W
∴ Electrical current = `P/V = 100/200 = 1/2` Amp
∴ Electrical resistance `R = V/I = 200/("I/2") `= 400 Ω
if five bulbs are connected in series to 200V
∴ Total resistance RT = 400 + 400 + 400 + 400 + 400 = 2000Ω
Current flowing thorugh a bulb `I = 200/2000 = 0.1 A `
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