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)`.

Options

A. `1.190 kg`
B. `3.20 kg`
C. `4.2 kg`
D. `0.25 kg`

Answer

A

Explanation

Net resistance of circuit , `R = (10 xx 5)/( 10 + 5) + (10 xx 5)/( 10 + 5) = (20)/(3) Omega`
Heat generated in circuit per minute is
`Q = I^(2) R t = (10)^(2) xx ( 20)/(3) xx ( 10 xx 60)`
` = 4 xx 10^(5) J = ( 4 xx 10^(5))/( 4.2 xx 10^(3)) kcal`
`m = (Q)/(L) = ( 4 xx 10 ^(5))/( 4.2 xx 10^(3) xx 80) = 1.19 kg`