A shunt generator has a critical field resistance of 200 ohm at a speed of 800r.p.m. If the speed of the generator is increased to 1000r.p.m., what is the change in critical field resistance of the generator?

A

Decrease to 160 ohm

B

Remains the same at 200 ohm

C

Increases to 250 ohm

D

Increases to 312.5 ohm