You hold in your hand a block of material with 3x10^27 protons , 3x10^37 neutrons , and 3.1x10^27 electrons. what is the mass of the block , and what is its charge

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

If gases like carbon dioxide and methane make up less than 1% of the total atmosphere, why is it important for scientists to monitor changes in percentages of these gases?

What is special about a dc circuit ?