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Heat

The specific ...

Question

The specific latent heat of fusion of ice is $80 c a l g^{- 1}$ . An immersion heater of power $25 W$ is kept in $100 g$ of ice at its melting point. If the heater is switched ON, then the time after which the temperature of ice starts raising.

$320 m i n$

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$320 s$

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$8.3 m i n$

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$22.4 m i n$

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Solution

The correct option is D
$22.4 m i n$

Step 1 : Given
Mass of ice , m $= 100 g$
Specific latent heat of fusion , c $= 80 c a l g^{- 1}$
Temperature , $∆ t = 4.2 ° C$
Power , P $= 25 W$
Step 2 : Calculate the thermal energy
$\begin{array}{l} Q = m c Δ t \\ Q = 100 \times 80 \times 4.2 \\ Q = 33, 600 J \end{array}$
Step 3 - Calculate the time required to raise the temperature
$P o w e r = \frac{E n e r g y}{t i m e} T i m e = \frac{E n e r g y}{p o w e r} t = \frac{Q}{P} t = \frac{33600}{25} t = 1344 s e c (∵ 1 m i n = 60 s e c) t = \frac{1344}{60} m i n t = 22.4 m i n$
Hence , after $22.4 m i n$ the temperature of the ice starts rising.
Hence option D is correct.

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Similar questions

An immersion heater of power $20 W$ just keeps $200 g$ of solid metal at its melting point. The heater is switched ON and temperature starts raising after $4 m i n$ , then the specific latent heat of fusion of the metal is ________.

Q. A piece of ice of mass

50 g

exists at a temperature of

- 20^{\circ} C

. Determine the total heat required to convert it completely to steam at

100^{\circ} C

. (Specific heat capacity of ice

= 0.5 c a l / g^{\circ} C

; specific latent heat of fusion for ice

= 80 c a l / g

and specific latent heat of vapourisation for water

= 540 c a l / g

)

Q. 400 g of ice at 253 K is mixed with 0.05 kg of steam at

100^{o} C

. Latent heat of vaporisation of steam

= 540 c a l g^{- 1}

. Latent heat of fusion of ice

= 80 c a l g^{- 1}

. Specific heat of ice

= 0.5 c a l g^{- 1}^{o} C^{- 1}

. Find the resultant temperature of the mixture.

150 g

of ice is mixed with

100 g

of water at temperature

80^{o} C

. The latent heal of ice is

80 c a l / g

and the specific heat of water is

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. Assuming no heat loss to the environment, the amount of ice which does not melt is :

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specific heat of fusion of ice

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The specific latent heat of fusion of ice is 80calg-1. An immersion heater of power 25W is kept in 100g of ice at its melting point. If the heater is switched ON, then the time after which the temperature of ice starts raising.

The specific latent heat of fusion of ice is $80 c a l g^{- 1}$ . An immersion heater of power $25 W$ is kept in $100 g$ of ice at its melting point. If the heater is switched ON, then the time after which the temperature of ice starts raising.