Correct Answer - Option 3 : Magnetic field decreases, speed increases
Concept:
If a load in a generator decreases i.e., load current decreases.
As the load demand decreases, the demand in current decreases, the excitation of the system decreases the density of the magnetic flux by decreasing the current in the generator field.
Therefore, if the load decreases, magnetic flux density decreases.
→ If the load on a power system decreases, the load current on the system decreases, which results in decreased armature current in the generator. This decreased armature current results in the decreased magnetic field in the armature. The rotor (field magnets) located in this armature magnetic field will then experience less attractive force will in effect increases the speed of the rotor, which in turn increases the voltage.
Therefore, it will result in a decrease in the magnetic field and an increase in speed.
