A 220 V shunt motor runs at 900 rpm. Flux reduced to 75% of rated; find new speed.

Option 1: 675 rpm

Option 2: 900 rpm

Option 3: 1100 rpm

Option 4: 1200 rpm

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Correct Option: 4

Explanation

N ∝ 1/ϕ. Flux = 0.75ϕ therefore N₂ = N₁/0.75 = 900/0.75 ≈ 1200 rpm.