Which is true regarding ac current? the electrons move back and forth. the +/- polarity is constant. it is common in portable devices. it can only produce low voltages.

In order to place a satellite into orbit, it requires enough fuel to supply the necessary mechanical energy. into what types of mechanical energy does the fuel get transformed?

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

During takeoff, the sound intensity level of a jet engine is 170db at a distance of 34 m. what's the sound intensity level at a distance of 1.0 km?