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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What is the significance of B-H curve?
H is the symbol for magnetic field strength, which is defined as the magnetomotive force per unit length of a magnetic circuit, where the magnetomotive force is provided by a current-carrying coil, wound around that magnetic circuit. Magnetomotive force is the product of the current flowing through the coil and the number of turns, expressed in amperes (although often spoken as "ampere turns").
The magnetomotive force gives rise to the magnetic flux within the magnetic circuit, the intensity of which is termed flux density (symbol B), expressed in teslas.
A B-H curve plots changes in a magnetic circuit's flux density as the magnetic field strength is gradually increased. The resulting shape indicates how the flux density increases due to the gradual alignment of the magnetic domains (atoms, that behave like tiny magnets) within the magnetic circuit material. When all the domains have aligned, the B-H curve reaches a plateau and the magnetic circuit is said to be saturated. At this point, any further increase in magnetic field strength has no further effect on the flux density. Different magnetic materials, such as iron, steel, etc., have B-H curves with different slopes and points at which saturation occurs.
After reaching saturation, a reduction in the magnetic field strength results in a reduction in the flux density. However, the resulting curve does not quite match the original curve, but 'lags behind' it. This effect is called hysteresis, which is from the Greek, meaning to 'lag behind'.
When the magnetic field strength reaches zero, the resulting curve indicates that the flux density has not, itself, reached zero. The value of flux density remaining is termed the remanence (or residual magnetism) of the magnetic material. 'Soft' magnetic materials, used in the manufacture of transformer cores, etc., will have a very small remanence; whereas 'hard' magnetic materials, used in the manufacture of permanent magnets, will have a very high remanence.
In order to remove any remanence, the magnetic field strength requires to be reversed (by reversing the direction of the current in the coil) and increased in the opposite direction. The amount of 'negative' magnetic field strength necessary to completely remove the remanence is called coercivity.
If we continue to increase the negative magnetic field strength, the magnetic material will again reach saturation in the opposite direction, and the new curve will be a mirror image of the original curve. The complete B-H curve is then usually described as a hysteresis loop. The area contained within a hysteresis loop indicates the energy required to perform the 'magnetise - demagnetise' process.
'Soft' magnetic materials require relatively little energy to become magnetised and demagnetised and, so, have 'narrow' hysteresis loops, whereas 'hard' magnetic materials require a great deal of energy and have 'wide' hysteresis loops.
So, B-H Curves and Hysteresis Loops are a valuable tools for comparing the characteristics and behaviour of different magnetic materials, in order to select them for an appropriate application.
What cannot be considered a single phase?
A heterogeneous mixture, such as a salad with different vegetables, cannot be considered a single phase. It contains distinct regions with different compositions and properties, making it a multi-phase system.
The recommended cable size for 210 amps would be at least 2/0 AWG (00 AWG) for optimal performance and safety. Make sure to consult the National Electrical Code (NEC) or a professional electrician to determine the exact cable size needed based on the installation requirements and conditions.
Does increasing the voltage to an electric heater increase the amperage it draws?
It will increase the current since the water heater is made of a heating element and which is resistive in nature.
Ohms law states that V=IR where V is the voltage, I the current and R the resistance.
Now the resistance will always remain constant. Thus, when the voltage is increased, the current will also increase.
What is the effect of load resistance on ripple voltage in presence of filter capacitor?
Ripple voltage, in the presence of a filter capacitor, is inversely proportional to load resistance.
If the load were zero (resistance infinite), then there would be no ripple voltage. As the load increases (resistance decreases), the ripple voltage increases.
The ripple waveform will appear to be sawtooth, with the rising edge following the input AC from the diode's conductioin cycle, and with the falling edge either being linear or logarithmic, depending on load. If the load is resistive, without a regulator, the falling edge will be logarithmic. If the load is constant current, such as with a regulator, the falling edge will be linear.
Why are center tapped transformers used in North America?
Center tapped transformers are used in North America to be able to use two voltages from the transformers secondary. It is known as a three wire system. Appliances circuits that utilize 240 volts and appliances that use 120 volts can be supplied from one transformer. The transformers secondary is center tapped and grounded. This allows the 240 volt winding L1 - L2 to produce 120 volts from one leg of the winding to ground L1 - N and the second half of the winding 120 volts from N - L2.
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Center tapped transformers are used anywhere world wide where ever they were designed to be used.
There is nothing particular to a center tapped transformer that makes it more or less suitable for use in North America.
How do you increase your single phase supply from 50 to 100 amps?
Put a second, identical unit right next to it and run them in parallel. If your single phase supply is designed to produce X volts and Y amps, you cannot produce more than Y amps with it without burning it up.
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Check with your electrical inspection department before doing the above fix. There is a new main breaker to take into account that has to be changed out from a 50 amp breaker to a 100 amp breaker. This process will involve the disconnection from the utility company and a reconnection which they will not do unless an electrical permit has been taken out and an inspection made.
To do this job yourself you have to know wire sizes, ampacity of wires and proper electrical workmanship. Such a project should be left to a licensed electrical contractor to take out the proper permits and call for proper inspections. By taking this route it will leave you confident that if any mishaps happen to the installation down the road your insurance company will be behind you 100%.
Some people will define the cause of an electrical fault as a "short circuit" but that is too simple an explanation because it doesn't explain how it is caused.
An electrical fault is the name given to any situation where some electrical current goes where it was not intended to go.
This situation can be caused by damage to the protective insulation around a wire - or around some other part - which puts the wire or part in contact with a different wire or part that it was not designed to touch because a difference in voltage has to exist between them to allow an item of electrical equipment to do its work.
If an item of electrical equipment gets dropped accidentally - or if something else hits it violently - that action can easily damage the insulation material or close an air gap that was designed to keep two parts electrically separate within that item of equipment.
Another way an electrical fault can be caused is by physical deterioration of some insulation. Such deterioration can be caused by many factors such as, for example, the temperature of the equipment being too high or if some unprotected equipment is exposed to wet or damp conditions. Such factors can put stresses on the insulation which it was not designed to withstand and it breaks down and causes an electrical fault to occur.
If an item of electrical equipment (or an electrical wiring circuit which connects different pieces of equipment together) is properly designed, then, if an electrical fault occurs, protective circuit breakers should trip and/or fuses should blow to stop the flow of any excessive current that is the result of the electrical fault, thus helping to prevent any fires and/or explosions from happening because the fault occurred.
How do you identify terminals of BJT?
The terminals of a BJT (bipolar junction transistor) are the emitter, base, and collector. One common method to identify these terminals is to look at the physical package of the transistor. The emitter is usually connected to the most heavily doped region and is often indicated on the package. The base is usually the middle terminal, and the collector is often connected to the remaining terminal.
Armature amps refer to the current flowing through the armature winding of an electric motor or generator. It is used to power the electromagnetic coils that generate the magnetic field needed for the motor or generator to operate efficiently. Monitoring armature amps is crucial for maintaining the proper functioning and performance of the motor or generator.
What will be input and output current of 10 KVA 3 phase UPS?
A 10 KVA 3-phase UPS will have an input and output current that depends on the specific voltage of the system. You can calculate the current by dividing the apparent power (in this case 10 KVA) by the square root of 3 multiplied by the voltage. For example, for a 208V system, the input and output current would be approximately 28.8 amps.
Yes, a motor is considered an inductive load because it operates by using an electromagnetic field to convert electrical energy into mechanical energy. This results in the motor drawing current that leads the voltage due to the inductive characteristics, causing a phase shift between the current and voltage waveforms.
The mathematical equation describing the relationship between electric current, voltage, and resistance was discovered by George Ohm in the 1820s. Ohm's Law states that current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R), expressed as I = V/R.
What is the cost of a miniature circuit breaker?
In the US a miniature circuit breaker, sold in a single unit, is about 15$, about the same as a regular breaker. If sold as a double unit, meaning two mini breakers installed into one housing, then it is about 25$.
Is a short circuit the easiest path for electricity to follow?
Yes, a short circuit provides the easiest path for electricity to flow because it bypasses the normal load and creates a low-resistance path between the two points. This can lead to high current flow and potential damage to the circuit or equipment.
How does the GFCI prevent serious injury from electric current?
Inside the GFCI is an electrical device that constantly compares the current on the two wires of an electrical circuit. If, at any time, the electrical device detects an imbalance, the GFCI shuts off the circuit.
Most electrical shocks occur when a person touches the LIVE wire of a circuit while grounded in some other way (such as standing barefooted on concrete). The GFCI detects that imbalance and shuts off the circuit so quickly that we often don't even feel the shock.
As a word of caution, don't depend on the GFCI as a substitute for common sense. If you aren't touching some kind of grounded surface, the GFCI will not function. In that situation you are nothing more than another resistance load. Also, if you feel that the GFCI will protect you and ignore normal caution around electricity, you may encounter a circuit that is either NOT protected with a GFCI, or you may encounter a GFCI that has failed. Either way, always use caution when doing anything with electricity.
Can impedence inversion be obtained by a short circuit stub?
No, impedance inversion cannot be achieved with a short circuit stub. A short circuit stub will have a low impedance at the point where it is connected, which will not invert the impedance at that point. Impedance inversion can be achieved using techniques such as a quarter-wave transformer or a transmission line with specific impedance characteristics.
Why the protection relay is more effective then circuit breaker?
They are used in two completely different ways in the System. starter relays for example ,uses a low current to pull core and close high current contacts needed for straiting only, or blower motor Relay's Circuit breaker can protect entire systems in your whole house , if one phase over loaded they are mechanically set up so that both phases will trip. on auto's they are used as switches to close the two heavier gauge wire for the load. fusible links in auto's are made to protect entire systems. note: in homes circuit breakers can also protect individual circuits. Not only the whole house (MAIN BREAKER).
What table in NEC would use to find FLC of a 3 phase motor?
To find the full-load current (FLC) of a 3-phase motor, you would refer to Table 430.250 in the National Electrical Code (NEC). This table provides the FLC values for various types and sizes of motors.
Can you perform a voltage drop test on AC as in DC?
Yes, you can perform a voltage drop test on AC circuits similar to DC circuits. However, you need to use specialized equipment designed for measuring voltage drop in AC circuits, which takes into account factors like impedance and phase difference. The principles of voltage drop testing remain the same, where you measure the difference in voltage between two points to identify any resistance or impedance in the circuit.
Relative density is a scalar (dimensionless) value. It is a unit-less number.
Relative density is the numerical ratio of the density of a given material compared to a standard, which is the density of water. So a relative density of 3 would indicate a material whose mass for a given volume is three times as great as the mass of an equal volume of water.
What unit do you get when you multiply coulombs by volts?
A charge equivalent to 1 V is equal to 1 J/C (that's Joules per Coulomb). There is no way, however, to do a straight conversion from volts to Coulombs as they measure slightly different properties.
Hope that helps! Happy Physics!
Maximum power is transferred from a source to a load when the load resistance is equal to?
A:is equal to the source
What is the difference between short to Battery and Open Load?
Related to a battery and open load is the battery just sitting there without anything connected. A short is a very low resistance attached to the tow terminals of the battery. For example, a wire connected across the battery terminals would constitute a short.
What is the purpose of conducting sc and oc test of single phase transformer?
The purpose of conducting sc (short circuit) and oc (open circuit) tests on a single-phase transformer is to determine its equivalent circuit parameters, such as the winding resistance, leakage reactance, and magnetizing reactance. These tests help to evaluate the transformer's performance and efficiency under various operating conditions.
