SSC JE Electrical Engineering 2012 Solved Paper

Electro magnetic torque
T=Kϕ1‌cos‌ϕ
where k is designed constant = (PZ/2πA)
where
P = number of poles
Z = Total number of amature conductor
N = rotation speed of the armature in revolution per minute (r.p.m.)
A = number of parallel paths
Now the flux ϕ is increased by 100% i.e.
ϕ2=ϕj+100%ϕ1=2ϕ1
I2=0.75I1
T1∝ϕ1I1‌cos‌45° &
T2∝ϕ2I2‌cos‌30° &
T2∝ϕ2I2‌cos‌30° =2ϕ1×0.75I1×cos‌30°

T1

T2

=

1×cos‌45°

2×0.75×cos‌30°

= 0.544
⇒T1=0.544T2
Then T2=1.838, T1=183.7%ofT1
Hence, the Torque increases to 183.7% of the original.