Question

A heater coil connected to 220 V has a resistance of 80 ohms. If the coil is plugged in for a time 't seconds' such that 1 kg of water at 20° Celsius attains a temperature of 60° Celsius. Find :
(a) the power of the heater
(b) the absorbed by water (in Joules)
(c) the value of 't' in seconds

I have my science board exam on 4th March. Today's paper was first class. Please anyone help me out in this question.

Answer 1

Answer:

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Answer 2

Answer:

(i) power of heater

= V^2/R = 220 x 220 / 80 = 500 W

(II) Heat absorbed by water , H = m * C * theta r [ where m = mass , C = specific heat of water = 4200 J/kg degree C and theta r = change in temp = 60 - 20 = 40 degree Celsius.]

= 1 x 4200 x 40 J

= 168000 J

= 168 kJ

(iii) Energy consumed by heater,

H = p x t

168000 = 500 x t

t = 168000/500

t = 336 s

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