Which of the laws of motion states to every action there is an equal but opposite reaction letter a newton's first law see newton's third law newton's second law or the law of conversation of momentum

Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects.

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete