Question

An AC generator spinning at a rate of 750 rev/min produces a maximum emf of 45 V. At what angular speed does this generator produce a maximum emf of 120 V? 

Answer 1

Data: e₁ = 45 V, f₁ = 750 rpm, e₂ = 120 V

e = NABω = NAB(2πf)  ... (∴ e ∝ f)

∴ `e_2/e_1 = f_2/f_1`

∴ `f_2 = e_2/e_1 xx f_2`

= `120/45 xx 750`

= `8/3 xx 750`

= 8 × 250

= 2000 rpm