A `500 W` heating unit is designed to operate from a `200 V` line . By what percentage will its heat output drop if the line voltage drops to `160 V`? Find the heat produced by it in `10 min.`
Text Solution
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Here, P = 500 watt, V = 200 V `:.` Resistance of heating unit, `R = V^(2)/P = (200)^(2)/500 = 80 Omega` When voltage drops to 160 volt, then heat produced per second `= V'^(2)/R = (160)^(2)/80 = 320 watt` `:.` Drop in heat production per second = 500 - 320 = 180 watt. `:.` % Drop in heat production per second `= 180/500 xx 100 = 36%`
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