Question

12. For water at 0°C it takes one hour for first 3 mmof ice layer formation. How much time will it takefor next 6 mm of ice formation?(1) 2 hour(2) 4 hour(3) 6 hour(4) 8 hour​

Answer 1

Answer:

(1)2hour

Explanation:

because already 3 mm is made to pass the 3mm of ice it takes one hour and the other for making another 3mm of ice

Answer 2

Answer:

4 option

Explanation:

we know, dQ/dt = KA ∆T/x

amount of water converted into ice at time dt , dm = ρA dx

now, energy required to convert water into ice in dt time , dQ/dt = Lf ρA dx/dt

where Lf is latent heat of fusion.

so, Lf ρA dx/dt = KA dT/x

⇒∫x dx = (K∆T/ρ Lf) ∫dt , let constant , C = K∆T/ρLf

⇒x²/2 = C t + R , where R is also constant

here it is clear that, t ∝ x²

so, t1/t2 = (x1/x2)²

here, t1 = 2 hours , x1 = 3mm

t2 = ?, x2 = 6mm

then, 2/t2 = (3/6)²

⇒t2 = 8 hours

hence, option (4) is correct choice.