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ELEC MACH
| Term | Definition |
|---|---|
| What does a generator do | Converts mechanical energy to electrical energy |
| What does a motor do | converts electrical energy to mechanical energy |
| What are some applications of generators | Power plant, wind turbine |
| What are some applications of motors | Cranes, Engine room heavy load pumps, large capacity exhaust fans, vehicles |
| In linear motion what is x | position |
| In linear motion what is v | velocity |
| In linear motion what is a | acceleration |
| What is work | the force over a certain distance |
| what is power | the force times velocity |
| In rotational motion what is theta | angular position |
| In rotational motion what is w | angular velocity |
| In rotational motion what is alpha | angular acceleration |
| In rotational motion what is angular force | torque |
| In linear motion what is force | mass times acceleration |
| What is a magnetic field | an invisible force field generated by a magnet moving electric charge spinning electrons and changing electric field |
| What does Amperes law state | A current passing through a wire induces a magnetic field around the wire |
| What ways can you strengthen an electromagnet using amperes law | Increase number of coils, increase the current |
| What does Faraday's law state | When a magnetic field changes around a conductor, it induces an electromotive force that drives an electric current |
| When does an magnetic field change around a conductor according to faradays law | Whenever magnetic field changes with time while conductor remains stationary, the conductor or coil moves through a static magnetic field, changing current in conductor with moving magnetic field |
| What is the basis of a transformer action | A changing current produces a changing magnetic field. That changing field causes the magnetic flux through a stationary coil to change, inducing electromotive force |
| What does Len'z law state | When an EMF is generated by a change in magnetic flux according to Faraday's law, the polarity of the induced EMF is such that it produces a current whose magnetic field opposes the change which produced it. |
| What does Lorentz force principle, also the basis of motor action | a current-carrying wire in presence of magnetic field experiences induced force |
| What is the basis of a generator action | Principle 4: A moving wire in presence of a magnetic field has voltage induced in it. V=vBL |
| When is current induced in a generator | When it is moving perpendicular to the magnetic field |
| What is a magnetic circuit | The closed path through which magnetic flux flows, usually consists of items with high permeability |
| What is a magnetic flux | The total number of magnetic lines of force passing through a region in space or set-up in a magnetic circuit |
| What is magnetomotive force | The magnetic pressure which sets-up or tends to set-up magnetic flux in a magnetic circuit. |
| What is Magnetic Field Intensity | The force acting on north pole when placed at a point in the magnetic field |
| What is magnetic flux density | a measure of the number of magnetic lines of force cutting through a plane of a given area at a right angle |
| What is u (Mhe) | Magnetic permeability of materials |
| What is Permeability | Amount of magnetic field intensity required to produce a given flux density for a material, the property of a material that describes the ease with which a magnetic flux is established in a component |
| What is relative permeability | Ratio of materials permeability to that of free space or the measure of the magnetizability of materials |
| what is Reluctance | opposition to flux, similar to a resistor in an electrical circuit |
| What is Permeance | A measure of how easily a particular magnetic path carries flux, reciprocal of reluctance (analog to G, conductance in electric circuit) |
| What is MMF in an electrical circuit | a voltage source |
| What is flux in an electrical circuit | Current |
| What is reluctance in an electrical circuit | resistance |
| what is permeance in an electrical circuit | conductance |
| What is a magnetic circuit | A structure that includes windings, magnetic materials, and a air gaps |
| What is the saturation region | When no further increase in the magnetization happens beyond this point at the curve, curve is almost flat |
| What is the unsaturated region | flux changes linearly and very rapidly |
| what is the transition/knee region | The region between unsaturated and saturated regions. Where the curve bends |
| What is left in the core when mmf in produced | A magnetic field called residual flux |
| What might be applied to the core in the opposite direction to force residual flux to zero | coercive mmf |
| What does the value of core flux depend on | The amount of mmf at any given time, and previous history of flux in the core |
| What is hysteresis | The dependence on the preceding flux history and failure to retrace flux paths for magnetic materials also known as the lag of magnetic flux density behind the magnetic field strength |
| What does the magnetic hysteresis loop show | The behavior of a ferromagnetic core graphically as the relationship between B and H is non-linear |
| What is Retentivity | The power of retaining this residual magnetism |
| What is Coercive Force | The amount of reverse magnetic field which must be applied to a magnetic material to make the magnetic flux return to zero |
| What are the main hysteresis losses | energy loss because of the heat up of the core |
| What is hard steel used in | Permanent magnets |
| What is silicon steel used in | Making armature of DC machines, transformer core, starter of induction motors |
| What is wrought iron used for | Electromagnets |
| What does an air gap allow | Adding reluctance, changing the B-H curve allowing higher current and magnetic field delaying saturation, causing flux fringing, storing magnetic energy due to its low permeability, they linearize B-H Curve |
| What is fringing | Variation of magnetic reluctance causes magnetic flux to bulge in air gap |
| What is fringing effect | The effective cross-section area of air-gaps will be larger than the cross-section area f the iron core on either side due to this, results from the presence of air gaps in magnetic circuits |
Created by:
jmsallee
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