Disc windings are primarily used in

A semicircular disc rests on a horizontal surface with its top flat surface horizontal and circular portion touching down. The coefficient of friction between semi circular disc and horizontal surface is µ. This disc is to be pulled by a horizontal force applied at one edge and it always remains horizontal. When the disc is about to start moving, its top horizontal force will

A

Remain horizontal

B

Slant up towards direction of pull

C

Slant down towards direction of pull

D

None of the above

A disc is a spinning with an angular velocity $$\omega $$ rad/s about the axis of spin. The couple applied to the disc causing precession will be (where $$I$$ = Mass moment of inertia of the disc and $$\omega {\text{P}}$$ = Angular velocity of precession of the axis of spin)

A

$$\frac{1}{2}I{\omega ^2}$$

B

$$I{\omega ^2}$$

C

$$\frac{1}{2}I\omega \omega {\text{P}}$$

D

$$I\omega \omega {\text{P}}$$

Multilayer helical windings are commonly used in the transformers as high voltage windings

A

upto 20 kV

B

upto 50 kV

C

upto 80 kV

D

for 110 kV and above

The insulation between windings and grounded core and the insulation between the windings of the same phase is

A

minor insulation

B

major insulation

C

either of the above

D

none of the above

The moment of inertia of a thin disc of mass ‘m’ and radius ‘r’, about an axis through its center of gravity and perpendicular to the plane of the disc is

A

$$\frac{{{\text{m}}{{\text{r}}^2}}}{2}$$

B

$$\frac{{{\text{m}}{{\text{r}}^2}}}{4}$$

C

$$\frac{{{\text{m}}{{\text{r}}^2}}}{6}$$

D

$$\frac{{{\text{m}}{{\text{r}}^2}}}{8}$$

A circular disc rotates at n rpm. The angular velocity of a circular ring of same mass and radius as the disc and to have the same angular momentum is

A

n rpm

B

$$\frac{{\text{n}}}{2}$$ rpm

C

$$\frac{{\text{n}}}{4}$$ rpm

D

2n rpm

Compensating windings are used in D.C. generators

A

Mainly to reduce the eddy currents by providing local short-circuits

B

To provide path for the circulation of cooling air

C

To neutralize the cross-magnetizing effect of the armature reaction

D

None of the above

The cylindrical windings using circular conductors are used for current rating of

A

upto 20 A

B

upto 40 A

C

upto 60 A

D

upto 80 A

Is universally used for windings of electrical machines because it is easily workable without any possibility of

A

fracture

B

Silver

C

Steel

D

Aluminium

E

Copper

Helical windings are used in

A

distribution transformers

B

power transformers

C

shell type transformers

D

none of the above

Disc windings are primarily used in

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