The Earth's Rotation Rate Is Slowing Because Of

question 56

Multiple Choice

The Earth's rotation rate is slowing because of:

• A) radioactive decays in its core
• B) relativistic effects of gravity
• C) tidal forces from the Moon
• D) the gravitational force of the Sun
• E) gravitational drag from dark matter

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Definitions:

Variable-frequency Drive

A system used to control the speed of an electric motor by varying the frequency and voltage supplied to the electric device.

Motor Controller

A device that regulates the performance of an electric motor by varying parameters such as voltage and current.

PWM

Pulse Width Modulation, a technique used to control the amount of power delivered to an electrical device by varying the duty cycle of a pulse signal.

Four-quadrant

Refers to operating modes of a drive or control system that can handle both positive and negative directions of both power and torque in all four quadrants of operation.