If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density

If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density

A. increases
B. decreases
C. remains the same
D. doubles

Explanatory answer : B


Flux density = flux / area

So if area increases, flux density decreases.

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When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage

When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage

[A] increases
[B] decreases
[C] remains constant
[D] reaches zero


Answer: A

In a generator induced emf is proportional to speed hence if speed increases,induced emf also increases.

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Which alternator more suitable for high-speed system ?

Which alternator more suitable for high-speed system ?

A. Salient pole

B. non salient pole

C. Both (a)& (b)

D. none of these

Answer: non salient pole, because salient pole alternators are mechanically weak.

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Bundled conductor are mainly used in high voltage overhead transmission lines to-(GATE-EE-2003)

Bundled conductor are mainly used in high voltage overhead transmission lines to-(GATE-EE-2003)

A. reduce transmission losses

B. increasing mechanical strength of the line

C. reduce corona

D. reduce sag

Answer: to reduce corona

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A 4 point starter is used to start and control the speed of a (GATE-EE-2011)

A 4 point starter is used to start and control the speed of a (GATE-EE-2011)

(A) dc shunt motor with armature resistance control
(B) dc shunt motor with field weakening control
(C) dc series motor
(D) dc compound motor


Answer: option (A)

The armature current of DC shunt motor

Ia = (V- Eb) /Ra.

at the time of starting, Eb = 0. If the full supply voltage is applied to the motor, it will draw a large current due to low armature resistance.
A variable resistance should be connected in series with the armature resistance to limit the starting current.

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