The power absorbed (in watts) in overcoming the viscous resistance of a footstep bearing is

In a footstep bearing, if the speed of the shaft is doubled, then the torque required to overcome the viscous resistance will be

A

Double

B

Four times

C

Eight times

D

Sixteen times

In a footstep bearing, if the radius of the shaft is doubled, then the torque required to overcome the viscous resistance will be

A

Double

B

Four times

C

Eight times

D

Sixteen times

The torque required to overcome viscous resistance of a footstep bearing is (where $$\mu $$ = Viscosity of the oil, N = Speed of the shaft, R = Radius of the shaft and t = Thickness of the oil film)

A

$$\frac{{\mu {\pi ^2}{\text{NR}}}}{{60{\text{t}}}}$$

B

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^2}}}{{60{\text{t}}}}$$

C

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^3}}}{{60{\text{t}}}}$$

D

$$\frac{{\mu {\pi ^2}{\text{N}}{{\text{R}}^4}}}{{60{\text{t}}}}$$

Footstep bearing is an axial load bearing.

A

True

B

Thrust load

C

Shear load

D

None of the listed

What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts?

A

20%

B

80%

C

40%

D

50%

A rotor which is balanced statically but not dynamically is supported on two bearings L apart and at high speed of the rotor, reaction on the left bearing is R. The right side of the bearing is shifted to a new position 2L apart from the left bearing. At the same rotor speed, dynamic reaction on the left bearing in the new arrangement will

A

Remain same as before

B

Become equal to 2R

C

Become equal to $$\frac{{\text{R}}}{2}$$

D

Become equal to $$\frac{{\text{R}}}{4}$$

An 3 phase alternator star connected 400 V synchronous motor takes a power input of 5472 watts at rated voltage. Its synchronous reactance is 10** per phase and negligible resistance. If its excitation voltage is adjusted equal to the rated voltage of 400 V, its power factor is _______

A

cos(10°)

B

cos(20°)

C

cos(40°)

D

cos(30°)

The power output of an amplifier is 7 watts. The power gain is 80. What is the input power?

A

87.5mW

B

87.5W

C

13W

D

13mW

An amplifier is measured to have an internal resistance of 10 kΩ, voltage gain of 100V/V and output resistance of 100 Ω. Also, when a load resistance of 1 kΩ is connected between the output resistance if found to decrease to 8 kΩ. If the amplifier is fed with the signal source having an internal resistance of 2 kΩ. Find Gm.

A

1 A/V

B

10 A/V

C

100 A/V

D

1000 A/V

An amplifier is measured to have an internal resistance of 10 kΩ, voltage gain of 100V/V and output resistance of 100 Ω. Also, when a load resistance of 1 kΩ is connected between the output resistance if found to decrease to 8 kΩ. If the amplifier is fed with the signal source having an internal resistance of 2 kΩ. Find Av.

A

9.09 V/V

B

10 V/V

C

90.9 V/V

D

100 V/V

The power absorbed (in watts) in overcoming the viscous resistance of a footstep bearing is

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