How can we reduce electricity consumption in summer

 In summer the air is very hot and dry. The temperature  of  the  air can be reduced either by desert cooler or AC. Can we use the both? The desert cooler decreases the temperature very cost effectively but it increases the humidity. Here comes the role of AC. The AC will decrease the humidity. So by using the combination of desert cooler and AC does the cooling faster and cost effectively.

Why salt is added to make ice cream

 Adding salt decreases the freezing point of ice. We know pure ice melts at 0°C and if we add salt to it it starts melting at a lower temperature, let's say at -6°C. That means ice start melting at a faster rate than pure ice. That is why it is used in melting snow at roads. But do you wonder how is it helpful in freezing ice cream?

The answer lies in the huge difference in latent heat of melting and specific heat. The latent heat of fusion of ice is approx. 334 KJ/Kg while the specific heat of ice is 2.09 KJ/Kg°C. Let's consider an example, if we have 1 kg of an ice at -10°C. It will absorb 20.9 KJ heat from surrounding and start melting at 0°C. But if we add salt 100 gm of salt to 1 Kg of ice it will approximately decrease the freezing point to -6°C. So it will absorb 8.36 KJ of heat and reaches to -6°C and then start absorbing 334 KJ heat to melt. This means the temperature will be -6°C for quite long time and it will help infreezing ice cream.