4. The speed of a d. c. motor increases with increasing current through the armature coil. Given fixed supply voltage, two ways of changing the current supplied to the motor are: (1) a variable resistor (potentiometer) or (2) pulse width modulation (PWM). Explain how each method works. Provide one advantage and one disadvantage of each method.

are there answer choices to this question? this seems like a question where you have options to choose from.

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

hope this ! this is not copied! search it up, it's free of plagiarism!