What is the period of a wave that had a frequency of 10Hz

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.

Explain why electric current cannot exist if a current doesn't have a voltage source.

What is the relationship between the direction of motion of the balloon and the wind currents