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प्रश्न
Calculate the time taken by an immersion heater, which supplies energy at the rate of 7000 J/minute to raise temp. of 5 kg water from 22°C to 47°C.
उत्तर
`"Q"/"t"` = 7000 J/min
m = 5 kg
ΔT = 47 - 22 = 25°C
C = 4200 J/kg°C
Q = m x C x T
= 5 x 4200 x 25 = 525000 J
Time taken = `525000/7000` = 75 min
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