To calculate the change in temperature, subtract the initial temperature from the final temperature. Example: 84.2 degree Fahrenheit - 41 degrees Fahrenheit = 43.2 degrees Fahrenheit. The temperature from morning to afternoon changed by 43.2 degrees Fahrenheit.
It needs 12 volts so it will be the standard modern power supply provides 12 volts of power.
Almost all electrical appliances come for a standard voltage. Depending where you live, this is usually about 110 volts in some areas, and about 220 volts in other areas. You can take a look at a specific appliance; there is usually a metallic sticker that has the electrical specifications.