A heating curve has been plotted for a solid object as shown in the figure. If the mass of the object is $200 g$ , then latent heat of vaporization for the material of the object is $\frac{n}{2} \times 10^{6} J / k g$ . If power supplied to the object is constant and equal to $1 k W$ , then find the value of $n$ .

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Solution

We know that: $Q = m L$
Given:
$m = 200 g, L = \frac{n}{2} \times 10^{6} J / k g, P = 1 k W$
Heat used for evaporation from graph is
$2500 - 1600 = 900 k J$

Mass evaporated is $0.2 k g$

We know that $Q = P t = m L$
$L = \frac{P t}{m}$

$L_{v} = \frac{900 \times 10^{3}}{0.2} = \frac{9}{2} \times 10^{6} J / k g$

Comparing with $\frac{n}{2} \times 10^{6}$
$n = 9$

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Standard VIII Physics

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A heating curve has been plotted for a solid object as shown in the figure. If the mass of the object is 200g, then latent heat of vaporization for the material of the object is n2×106J/kg. If power supplied to the object is constant and equal to 1 kW, then find the value of n.

We know that: Q=mL Given: m=200g,L=n2×106J/kg,P=1 kW Heat used for evaporation from graph is 2500−1600=900 kJ Mass evaporated is 0.2 kg We know that Q=Pt=mL L=Ptm Lv=900×1030.2=92×106J/kg Comparing with n2×106 n=9