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Thermodynamics

# A $5\; kg$ object is heated by a $50\; W$ power source . If the specific heat capacity of the object is $\;50 Jkg^{-1}K^{-1}\;$ , after what time will the temperature rise by $\;50^{0}C\;.$

$(a)\;4\;mins\;40\;s\qquad(b)\;4\;mins\;20\;s\qquad(c)\;3\;mins\;10\;s\qquad(d)\;4\;mins\;10\;s$

Answer : $4\;mins\;10\;s$
Explanation :
Total energy required to raise the temperature by $\;50^{0}C=5 \times 50 \times 50$
$=12.5 kJ$
Let ' t ' be time required by heat source to provide this energy
$=50 \times t=12.5 \times 10^{3}$
$t=250 s$