If Rotational Velocity Of A Dynamo Armature Is Doubled Then Induced Emf Will Become What Is Increased In Step Down Transformer

If rotational velocity of a dynamo armature is doubled, then induced emf will become…… What is … Two times (c) Four times (d)…


The correct option (b) Two times 


emf induced = e = Esin ωt

rotational velocity is double i.e ω changes to 2 ω then

e’ = Eo sin 2ωt

= 2 Eo sin 2ωt ∙ cos ωt

 = 2e cos ωt

= 2e sin[ωt + (π/2)]

 If we consider magnitude then e’ = 2e i.e. induced emf is twice.