<span>Copernicus decided this with more of an educated guess than anything. For example is when your standing right next to a plane it's huge Right? Well when it's flying it looks really small. He used the same reasoning for stars. Since it looks small it must be farther away.</span>
Answer:
The third image
Explanation:
The one with the thumb pointing to the right
Calcium has 2 valence electrons
Answer:
Commutator is a ring which reverse the direction of current in AC circuit so that the coil connected to it will continuous to move in the same direction.
Explanation:
In motors there exist a coil which is rotated due to torque of magnetic field when current flow through it. Since AC current is used to run the motor so we know that AC current changes its direction after half cycle.
So here commutator plays an important role to reverse the direction of current after every half cycle so that the current goes in same direction always into the coil.
This will produce a constant direction torque on the coil so that it will rotate in same sense always.
So commutator role is to provide same direction current to the coil by reversing its direction after every half cycle
