Question

An electric kettle used to prepare tea, takes 2 minutes to boil 4 cups of water (1 cup contains 200 cc of water) if the room temperature is 25°C. (a) If the cost of power consumption is Re 1.00 per unit (1 unit = 1000 watt-hour), calculate the cost of boiling 4 cups of water. (b) What will be the corresponding cost if the room temperature drops to 5°C?

Answer 1

Answer:

I don't know the answer

Answer 2

(a)The cost of 4 cups of boiling water is Rs. 0.7.

(b)If the room temperature drops to 5 degree Celsius, the corresponding cost is Rs. 0.09.

Explanation:

(a) For boiling 4 cups of water, the time taken in t = 2 minutes .

Volume of boiled water is 800 cc.

Initial temperature would be 25 degree Celsius and the final temperature is 100 degree Celsius.

The change in temperature would be 75 degree Celsius.  

Then, the mass of boiled water is 800 x 1 = 800g. For boiling the water, the required heat is $Q=m s \vartheta=252000 \mathrm{J}$  

It is known that $1000 watt - hour =1000 \times 3600 watt sec.$ So, for boiling water, the cost is Rs. 0.7.

(b) Initial temperature is 5°C; Final temperature is 100°C. Change in temperature is shown as 95°C. So, the cost of 4 boiling cups of water is Rs. 0.09.