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Four resistances carrying a current shown in Fig. `7.41` are immersed in a box containing ice at `0^(@)C`. How much ice must be put in the box every `10 min` to keep the average quantity of ice in the box constant? Latent heat of ice is `80 calg^(-1)`.

Text Solution

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The equivalent resistance of the circuit is
`R = ( 10 xx 5)/(10+5) + (5 xx 10)/(5+ 10) = 10/3 + 10/3 = 20/3 Omega`.
Heat produced in 10 min.
`H = (i^(2)Rt)/J = ((10 xx 10) xx 20 xx (10 xx 60))/(3xx4.2) cal`
Let m be the mass of the ice melted in 10 minutes
Then, `m xx 80 = (10 xx 10 xx 20 xx10xx 60)/(3xx4.2)`
or ` m = (10 xx 10 xx 20 xx10xx 60)/(80 xx 3xx4.2)`
` = 1190` gram
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