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'Residual magnetism' isn't something that's 'necessary'; rather, it's something you're stuck with, whether you want it or not! Residual magnetism is due to a phenomenon called 'hysteresis', which is derived from a Greek word, meaning 'to lag'.
A bit of background first. If we were to wind an insulated coil around the sample of ferromagnetic material, and pass a current through that wire, we would create and apply magnetic field strength (symbol: H), expressed in amperes per metre, to that sample. This results in a magnetic field being set up within the sample, the intensity of which we call its flux density (symbol: B) expressed in teslas.
If we gradually increase the magnetic field strength, the resulting flux density would also increase until a point, called 'saturation' is reached -at this point any further increase in magnetic field strength will NOT increase the flux density. If we were to graph this behaviour, then the result would look something like an elongated 'S', rather than a straight line. This graph is known as a B-H curve.
Now, if we were to reduce the magnetic field strength to zero, the magnetic flux density would also reduce towards zero (following a slightly-different curve) but would not reach zero when the magnetic field strength reaches zero -in other words, when we remove the magnetic field strength, the sample 'retains' some flux density -and we call this 'residual magnetism' or, more accurately, 'residual flux density' or 'remanance'. This is what we mean by 'hysteresis' -i.e. changes in magnetic flux density lag behind changes in magnetic field strength.
To remove this residual flux density, we would actually need to reverse the direction of the magnetic field strength (by reversing the direction of the current through the coil) until the flux density falls to zero.
Different ferromagnetic materials have different values of residual flux density. For example materials that make good permanent magnets have very high values of residual flux density while others, such as metals used to make transformers, electromagnets, etc., have very low values of residual flux density.
To summarise, residual magnetism is something that occurs naturally and the amount of residual magnetism depends on the type of magnetic material involved. It's not a matter of being 'necessary', it's simply a characteristic of ALL magnetic materials.
What else can I help you with?
If a selfexcited generator has lost all of its residual magnetism can it build up an output voltage?
yes
Why dc shunt generator can not induce any voltage with rated speed?
Two things could have occurred. (1) wrong direction of rotation causing loss of residual magnetism or (2) loss of residual magnetism over long period of no use. can be remedied by "flashing" the shunt field winding howlumf
What are the causes of failure of d.c shunt generator to excite?
no residual magnetism in the stator. this can happen with an overload which will occasionally even reverse the output polarity
Would the motor turn if only the armature were excited?
A motor will turn when only the armature is excited, if there is enough residual magnetism in the field.
What is residual voltage for DC generator?
This case arises only in series dc generator current should be sent around the poles to magnetize. this current can the source(generator). current is passed through poles if it is loaded. but if it is not loaded current is zero through the field. load voltage should be zero actually.but this dont happen.we use generator frequently.due to this poles are partially magnetized this causes some voltage appear called residual voltageAnswerThere's no such thing as 'residual voltage'; you're confusing it with 'residual magnetism', which exists in the magnetic poles of a self-excited d.c. generator and which enables the build-up of its terminal voltage.
How residual magnetism present inside the self excited generator?
Residual magnetism in a self-excited generator refers to the small amount of magnetism that remains in the magnetic core after the generator has been de-energized. This residual magnetism is crucial for the initial excitation of the generator because it provides the necessary magnetic field to induce voltage when the generator is started. As the rotor turns, the residual magnetism induces a small voltage in the stator windings, which, when connected to the field windings, enhances the magnetic field and leads to self-excitation, allowing the generator to generate power. Without sufficient residual magnetism, the generator may fail to start or produce voltage.
What is difference between residual magnetism and retentivity?
Residual magnetism and remanence are the same thing. The term residual magnetism is often used in engineering applications. Both terms describe the magnetization, and measure of that magnetism, left behind in a ferromagnetic material after the external magnetic field is removed.
What is residual magnetism?
Residual magnetism is the magnetism that remains in a material even after an external magnetic field is removed. This phenomenon is commonly observed in magnetic materials such as iron and steel after they have been magnetized. Residual magnetism allows these materials to retain some magnetization and can be useful in applications such as magnetic memory storage devices.
Can a shunt motor be started without residual magnetism?
Yes. The field is provided by the shunt windings, which are connected in parallel with the supply. You may be confusing a motor with a generator, as you cannot start a shunt generatorwithout residual magnetism.
The flux density that remains when the magnetizing force is removed is called?
residual magnetism
What is residual magnetisim?
It depends on the context in which you are referring to it, but basically Residual Magnetism is that magnetism remaining in the core of an electromagnet after the coil current is removed. In the widest use of the term, it could be used to refer to that magnetism left in a magnetically susceptible substance when it cools past its Curie point, (paleomagnetism is an example of this).
What is the residual magnetism of a rock called?
The residual magnetism of a rock is called "remanent magnetism" or "remnant magnetization." This refers to the magnetization that remains in rocks after the external magnetic field has been removed, often due to the alignment of magnetic minerals during the cooling or solidification process. Remanent magnetism is crucial for understanding the geological history of the Earth, including plate tectonics and the movement of continents.
How initially voltage build up in an alternator by residual magnetism?
The residual flux will help the phenomenon of changing flux. So that emf generation takes place.
If a selfexcited generator has lost all of its residual magnetism can it build up an output voltage?
yes
What is magnetism on Mars?
The magnetic field on Mars is only residual, it collapsed many eons ago.
For a 3 phase alternator why there is an AC voltage generated in the absence DC excitation?
due to residual magnetism
Is a36 steel magnetic?
A36 is paramagnetic. It is fairly good conductor of magnetic field, and it will be atracted to magnets strongly. As far as residual magnetism (can it be magnetized) I don't know for sure. I know you can not make usefully strong magnets out of A36 material, but it may have some residual magnetism.
