The diagram shows a simple electric generator that keisha is studying.

as keisha runs the generator, which best describes what should happen to the needle that measures electric current?

a. it will move to a large positive value and stay there.
b. it will move back and forth between 0 and a large positive value.
c. it will move back and forth between a large positive and a large negative value.
d. it will move to a large negative value and stay there.

In this kind of generators, Keisha has a wire that will rotate inside a magnetic field.
Since the electrical field generated depends on the inclination of the wire with respect to magnetic field lines, and this inclination varies with time, Keisha will get a varying electrical field, therefore also a varying electric current: the value will be zero when the wire is parallel to the magnetic field lines, the maximum positive value will occur when the wire is perpendicular to the magnetic field lines after one fourth of rotation, then again zero when the wire is parallel and the maximum negative value will occur when the wire is perpendicular to the magnetic field lines, but upside down, after three fourths of rotation.

Therefore, we expect the needle to move back and forth between a large positive value to a large negative value.  

My answer is opptionc, just check with anyone else