If an electric heater is rated at 1000, W , then time required to heat one litre of water from 20,^o

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10-1.Thermometry, Thermal Expansion and Calorimetry

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If an electric heater is rated at $1000\, W$, then the time required to heat one litre of water from $20\,^oC$ to $60\,^oC$ is

A

$1\, min\, 24\, sec$

B

$2\, min\, 48\, sec$

C

$4\, min\, 17\, sec$

D

$5\, min\, 36\, sec$

Solution

Heat required to heat $1 \mathrm{Lt}$

water $=m s \Delta \theta$

$=1 \times 4200 \times(60-20)$

$=4200 \times 40$

requred time $=\frac{4200 \times 40}{1000}$

$=42 \times 4=168$ $second$

i.e. $2 \,\,min\,\, 48 \,\,second$

Standard 11

Physics

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