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

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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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