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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
Are DC generators more expensive then AC generators?
DC generators require more time and material to make. Because of this, it will be cheaper to purchase an AC generator. DC generators are typically a better product as well, and you get what you pay for.
What are advantages of a series combination of resistors?
parallel combination of resistors are used in house circuits
How do you calculate total emf in parallel connected cells?
When connecting cells in parallel, it is important that they are all of the same type.
The total e.m.f. of cells connected in parallel is equal the the e.m.f. of an individual cell.
So, if each cell has an e.m.f. of, say, 1.5 V, then it doesn't matter whether you have one cell or a hundred cells, the e.m.f. of the resulting battery will also be 1.5 V.
How much current would an applied voltage of 10 volts cause through a resistance of 5 ohms?
10 volts applied to 5 ohms would cause a current flow of 2 amperes.
Current = voltage divided by resistance.
Is the line is necessary for the balanced star- connected load?
I think you probably mean is a neutral conductor necessary for a balanced star-connected load? If this is what you mean, then the answer is no, it isn't, as the phasor-sum of the phase currents will equal zero. Often, though, it is difficult to achieve a balanced load, so a neutral is then necessary, as it is needed to provide a return path for the unbalanced current -without this neutral, the phase voltages would change and become unbalanced.
How do you prevent shock by capacitors?
Discharge the capacitor, normally with a resistor accross the terminals (Calculated size)
Why do you represent leakage flux in a transformer by inductive reactance?
A transformer is often represented by an equivalent circuit, in which the transformer itself is considered to be 'ideal', and its basic losses are then represented as resistance and reactance in series with both the primary and secondary windings for a loaded transformer, or just on the primary side for a transformer on open circuit.
The transformer's primary flux comprises two components: the main flux, which links the primary and secondary windings, and a leakage flux which links just the primary winding. The leakage flux is considered arising from a self inductance in series with an 'ideal' primary winding. The reactance of this inductance is termed the primary leakage reactance. The voltage drop across this reactance will lead the primary no-load current by 90 degrees which, when added to the voltage drop across the resistance of the primary winding, acts to reduce the back emf of the primary winding below the value of the applied voltage and cause it to lag.
A similar explanation accounts for the an inductance and resistance in series with the secondary winding, when the transformer is loaded.
The term 'house earthing' is used in the electrical wiring of a structure in order to ground the house against electrical leakage which can cause increased power usage and the possibilty of safety concerns involving electrical shock.
Why may copper losses be neglected in the open circuit test of a transformer?
Because the magnetising current is very small, so the primary losses are insignificant, while there is no secondary current, so there are no secondary losses.
How do you calculate the rpm of a motor with a known number of poles and a frequency of 60 Hrtz?
A synchronous motor will spin at the system frequency. 60 Hz translates into 60*60 = 3600 direction changes per minute. If this is a two pole motor (one north and one south), it will spin 1 rotation per direction change. If it is a four pole motor (two north and two south), it will spin 1/2 rotation per direction change.
If this is an induction motor, it will spin at a frequency slightly less than an equivalent synchronous motor; this frequency difference is referred to as slip.
WHAT TYPE OF transformers has secondary current of the same order as the magnetising current?
A one to one, i.e. isolation, transformer.
CommentIt might be worth pointing out that the secondary current is determined by the load, and the primary current is then determined by the secondary current. The questioner appears to think that the secondary current is determined by the primary current.
The letter 'G' stands for 'giga' and its position represents the decimal marker. So, '5G' represents 5.0 gigaohms.
How do you define voltage gradient?
A voltage gradient or, more accurately, potential gradient, is the change in electric potential measured between a point of high potential and a point of low potential. It is normally measured with respect to one or other of these two points.
A practical example of a potential gradient can be demonstrated by connecting a variable resistor as a potentiometer. If an external voltage is applied across opposite ends of the potentiometer, then a potential gradient can be observed by connecting a voltmeter between one end of the potentiometer and its wiper terminal, and varying the position of the wiper. As the wiper is moved from one end of the potentiometer to the other, the potential will be seen to fall towards zero.
Can supply 660volt 50Hz by 660volt 60Hz?
It depends on the nature of the load. For example, a resistive load (e.g. heating) should be no problem whatsoever. But if the load involves magnetic circuits (i.e. transformers, motors, etc.), there may be a problem with overheating which could damage any insulation.
How do you use a capacitor as a power saver?
You cannot use a capacitor as a 'power saver' or, more accurately, 'energy saver'! A capacitor may improve the power-factor of a load, and this may reduce the value of its load current, but this does not reduce the energy consumed by the load. For a residence, a so-called 'power save' capacitor is nothing more than a rip-off.
What happenes to if you add more loads to a parallel circuit?
Adding additional branches will have no effect on the operation of any of the other branches, but the overall supply voltage will increase by the amount drawn by the additional loads.
What is the difference between off load tap changer and on load tap changer?
An on-load tap-changer must not break the supply to the transformer's windings while the transformer is on load. So it has a 'make-before-break' arrangement with its contacts -i.e. one contact moves to the second tap setting, before the second contact moves away from the first tap setting, while a reactor balances the load currents when the contacts are on different tap settings. An on-load tap changer is motor-driven, and can be operated automatically or manually.
An off-load tap-changer does not require a make-before-break arrangement, because it is designed to be operated when the transformer is disconnected.
What is shunt and series motor?
A series motor is one in which the field windings are in series with the armature windings. So the torque is proportional to the square of the supply current.
'Shunt' is an archaic term for 'parallel'. So a shunt motor is one in which the field winding is in parallel with the armature windings. So the torque is proportional to the supply current.
What happen when you reverse the direction of rotation in a separately excited dc generator?
When reverse the direction of a seperately excited DC generator,only polarities has been reversed,i.e., (+) becomes (-) and (-) become (+).
Why is there a harmonics when there is no load?
Harmonics is electric current or voltages that are part of the power system as a result of nonlinear electric loads. If there is no load and a harmonic is present it can present because of a rectifier in the system.
Why voltage is generated at lower value?
Are you are asking why an alternator's terminal voltage needs to be increased, using a transformer, for transmission?
The answer is that the voltage supplied by an alternator is determined by how many conductors can be inserted into its stator slots and this, in turn, is limited by the physical size of the alternator. So the output of alternators is limited to around 300 kV.
A single load doesn't really constitute either a series or a parallel circuit. You could argue that the lamp is in series with the supply, because the same current flows through both. But you could also argue that it is in parallel with the supply, as it shares the same voltage. So the terms 'series' and 'parallel' are only really used when to describe how two or more loads are connected to the supply.
