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Find the resistance of `240 V - 200` watt electric bulb when glowing. If this resistance is `10` times the resistance at `0^(@)C` and the temperature of the glowing filament is `2000^(@)C`, then find the temperature coefficient of resistance of the filament. |
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Answer» Resistance of hot bulb, `R_(t) = V^(2)/P = (200 xx 200)/100 = 400 Omega` Resistance of bulb at room temperature, `R_(0) = 400/10 = 40 Omega` Now, `R_(t) = R_(0) ( 1 +alpha t)` `:. 400 = 40 (1 +alpha xx 2000)` or `10 = 1 + alpha xx 2000` On solving, we get `alpha = 9/2000 = 4.5 xx 10^(-3).^(@)C^(-1)` |
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