Question

An electric geyser is used to heat 5l of water from 13℃ to 83℃ .If the heat lost in radiatin is 40 kj and water equivalent of geyser is 100 . Determine the efficiency of the geyser . Take specific heat of water as 4200 J/kg.k°.

Answer 1

Answer on Question #69792-Physics-Molecular Physics | Thermodynamics

An electric geyser is used to heat 5l of water from $13{}^{\circ}\mathrm{C}$ to $83{}^{\circ}\mathrm{C}$. If the heat lost in radiatin is $40\mathrm{kJ}$ and water equivalent of geyser is $100\mathrm{g}$. Determine the efficiency of the geyser. Take specific heat of water as 4200 J/kg.k°.

Solution

$$m = 5 L = 5 k g.$$ $$\Delta t = 83 - 13 = 70 K.$$

Total mass:

$$M = 5 + 0.1 = 5.1 k g.$$

Heat required:

$$Q = m c \Delta t = (4200)(5.1)(70) = 1.4994 \cdot 10^{6} J.$$

The efficiency of the geyser:

$$\eta = \frac{1.4994 \cdot 10^{6} - 40 \cdot 10^{3}}{1.4994 \cdot 10^{6}} = 0.9733 \text{ or } 97.33\%.$$

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