Two room heaters are marked 220 V, 500 W and 220 V, 800 W respectively. If the heaters are connected in parallel to 220 V mains supply, calculate:

(i) the current drawn by each heater.

(ii) the resistance of each heater.

(iii) total electric energy consumed in commercial units if they operate simultaneously for 2 hours.

Here V = 220 V, P₁ = 500 W, P₂ = 800 W

(i) Current drawn by 500 W heater,

straight I subscript 1 space equals space straight P subscript 1 over straight V space equals space 500 over 220 space equals 25 over 11 straight A space equals space 2.27 space straight A. space space space Ans.

Current drawn by 800 W heater,

straight I subscript 2 space equals space straight P subscript 2 over straight V space equals space 800 over 220 space equals space 40 over 11 straight A space equals space 3.67 space straight A. space space space Ans. space

(ii) Resistance of 500 W heater,

straight R subscript 1 space equals space straight V squared over straight P subscript 1 space equals space fraction numerator 220 space cross times space 220 over denominator 500 end fraction space equals space 96.8 space straight capital omega. space space space Ans. space

Resistance of 800 W heater,

straight R subscript 2 space equals straight V squared over straight P subscript 2 space equals space fraction numerator 220 space cross times space 220 over denominator 800 end fraction space equals space 60.5 space straight capital omega. space space space Ans. space

(iii) Total energy consumed in 2 hours

equals space straight P space cross times space straight t space equals space left parenthesis 500 space straight W space plus space 800 space straight W right parenthesis space cross times space 2 space straight h

equals space 1300 over 1000 space kW cross times 2 space straight h

equals space 2.6 space kWh. space space Ans. space

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