What are the two types of electrical circuits

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

The pilot of a helicopter hovers at an altitude of 1200 feet over a park. the angle of depression to the base of a statue is 17 degrees. the angle of depression to the nearest park exit, in line with the statue, is 14 degrees. to the nearest foot, what is the distance from the statue to the exit?

Aweather balloon has a volume of 52.5 liters at a temperature of 252 k. the balloon is released and rises to an altitude where the temperature is 295 k. how does this temperature change affect the gas particle motion?