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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 relevance of logic for electrical engineering?
Logic is reasoning. It is a thought process that seeks to arrive at a rational and sensible end, as opposed to an emotional one. It is a way to solve problems and arrive at solutions that will work in a particular situation. That is part of what electrical engineers do.
What is the current in a 10V circuit if the resistance is 2Ω?
If a resistor has a current of 2 amperes when connected to a single battery, connecting a second identical battery in parallel with the first will not change the current through the resistor.
This is because the voltage across the resistor will not change. Yes, the current capacity of the battery (pair) will double, but the voltage will not change.
The exception is if the battery does not have the capacity to supply 2 amperes without sagging in output voltage. In this case, adding the second battery will slightly increase the current through the resistor.
(By the way, without some kind of equalizing circuit, it is not a good idea to connect batteries in parallel. This is because slight differences in voltage could create substantial current flows through the batteries, and possibly damage, fire, and/or explosion.)
Voltage is a build up of electrons at one location relative to another location. To form a voltage gradient (difference), you need to somehow build up electrons at one location, or remove electrons from one location. Shuffling your feet on a thick carpet can do this!
How does a hydroelectric dam generate electricity?
A hydro dam works by taking the energy of water flow and converting it into an electric voltage. The water is regulated through a series of water turbines. The water flows through the turbine, pushing the turbine blades causing a rotation to a shaft. The shaft is then attached to an electrical generator. Inside the electrical generator, magnets are rotated around wire coil inductors which cause a voltage.
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The word 'hydro' means water. When water is stored in a reservoir by construction dam, the stored water will have gravitational potential energy. When water is allowed to flow down this PE is changed into kinetic energy. This KE will make the wheels of a turbine to rotate. This mechanical energy ie rotational energy is changed into electrical energy with the help of magnetic field. This phenomenon is known as electromagnetic induction, first found by Michael Faraday. This is how hydro power is changed into electrical power.
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The energy in moving (falling) water, is supplied by gravity, and the moving water has kinetic energy. This mechanical energy is applied to turbine blades, and the turbines turn electric generators to generate electricity.
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Hydro power is generated by using kinetic energy from flowing water to turn turbines in generators.
Turbine is moved with flow of water and this is coupled with generator to produce electricity
What is dc separately excited shunt generator?
Either or both can be separately excited. To generate voltage you need a big magnet( the field). Most generators use an electro-magnet. Now the electro-magnet needs a source of power (electricity). We could use the generators own output to excite the field (magnet), this is called self excitation. The problem with self excitation is that we have to wait for the generator to turn and start generating, also to start generating (Building up) there must be some left over magnetism from the last time it was run (called residual magnetism) or not even a little voltage will be generated to start the field current flowing. To solve these problems we could use separately excited. This means we must have a separate source of power to excite the field to produce the magnetism. Sometimes a battery or gasoline driven generator is used to excite the field of a very large generator to get it generating and then we can use some of the generated output to either recharge the battery or switch over to from the battery. In any case we have adjustable control of the generator all the time. This is why most generators are designed to be separately excited. And that is why you car has a voltage regulator. It wakes up the alternator when the engine is started by separately exciting it (the field) with the battery and then regulates the output voltage of the alternator as the engine changes speed with the driver's commands from the gas pedal.
Is there such a thing as 115V 3 phase?
No!
The concept of three phase alternating electricity refers to the relational phase differential of three alternating current single phase sine waves, each displaced 120 degrees of phase angle from the other.
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Addetion:
still the is a three wire DC transmission system.
usually DC transmission used for several resone but the most know one is when the transmission line is longer than 600 km
Are the voltage and current in phase in a circuit of pure resistance?
Assuming that by the question you mean a circuit with a resistance, but no inductance, or capacitance, then yes, the voltage and current will remain in phase.
Reasoning:
The formula V = IR or... Voltage is equal to Current multiplied by Resistance, is (should be!) well known by school students, however this formula assumes that voltage and current are each constants.
This formula can be extended to apply to voltages and currents that vary with time, as in the following equation:
V(t) = I(t) R
Since R will be a constant resistance expressed in Ohms (or more formally, an impedance that contains no imaginary part: a real number), there is nothing in the formula that could introduce a phase shift.
(See the related link below for a wikipedia article on impedance.)
What is the formula that describes the voltage current relationship in an inductor is?
Inductance = Magnetic Flux/Current = [ML2T-2A-1]/[A] = [ML2T-2A-2]
So, Dimensional Formula of Inductance = [ML2T-2A-2]
How do you put a switch into an existing lamp flex?
=== === You can add an on-off switch to the flex if you use a "torpedo" or similar shaped switch that has been designed to be used for this purpose. Here is how to install it into the flex: * unplug the light from the outlet! * open up the casing of the switch * where you want to insert the switch cut the outer cover of cable very carefully with a sharp knife * be careful not to nick any of the other wires * cut one of the wires - especially if there is a black wire, that is the one to cut * if there is no outer cover on the flex then just cut one of the two wires which make up the flex * only cut one wire, don't cut the other wire! Just leave it undisturbed. * on the cut wire strip back the insulation about 5mm on both sides of the cut * connect one side of the cut wire (from the plug) to one terminal of the switch * connect the other side of the cut wire (going to the light) to the other terminal of the switch * NEVER CONNECT ANY WHITE/NEUTRAL WIRE TO THE SWITCH TERMINALS! * Place the other, uncut, wire inside the casing of the switch, lying alongside the switch mechanism itself. If you also want to lengthen the cable then: * you'll need to wire up a plug with a new length of flexible cable containing a pair of BLACK and WHITE wires to plug into the outlet * cut off the existing plug supplied with the light from the end of its cable * wire the "hots" of both of the cables to the switch terminals as described above. * the white/neutral of the flex or cable coming from the new plug to must be joined to the white/neutral wire in the flex going to the light using a proper small connector for electrical wire - it must be small enough to fit safely into the switch casing alongside the switch mechanism without touching either of the switch terminals. (If you know how to use solder safely, you could solder the two neutral wires together.)
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
If you do this work yourself, always turn off the powerat the breaker box/fuse panel BEFORE you attempt to do any work AND always use a meter or voltage indicator
to insure the circuit is, in fact, de-energized.
How do you make generator output voltage stable?
Inside the generators junction box there will be termination points that the generator coils terminate on. On the inside of the lid of the junction box there should be a diagram for different connections allowed for that generator. By moving jumpers around across these terminals a variety of voltages can be obtained.
Why narrow gap semiconductors have large dielectric constant?
The dielectric constant measures how strongly the eletronic charge in the material can adjust to shield an external electric field, larger the dieletric constant, more effective is the screening. But for the electronic charge be able to adjust responding to the electric field, the electrons should be easily moved, which means that each electronic state will change assuming a polarized configuration. If the gap is large, the electric field can not mix the electronic states in the valence band with the electronic states in the conduction band, (think of perturbation theory, where the denominator will be of order of the band gap energy) so the electrons don't polarize much and the dielectric constant is small. On the other hand, in a metal, where the gap is zero, any small electric field mix the occupied states with the unoccupied ones, and we have a strong screening. The dielectric constant measures how strongly the eletronic charge in the material can adjust to shield an external electric field, larger the dieletric constant, more effective is the screening. But for the electronic charge be able to adjust responding to the electric field, the electrons should be easily moved, which means that each electronic state will change assuming a polarized configuration. If the gap is large, the electric field can not mix the electronic states in the valence band with the electronic states in the conduction band, (think of perturbation theory, where the denominator will be of order of the band gap energy) so the electrons don't polarize much and the dielectric constant is small. On the other hand, in a metal, where the gap is zero, any small electric field mix the occupied states with the unoccupied ones, and we have a strong screening.
Give one advantage of using a circuit breaker rather than a wire or cartridge fuse?
An electrical breaker is dual function an electrical fuse just has one purpose.
Can you explain how a voltmeter and ammeter work?
In parallel with the element you wish to measure the voltage across.
Which of what following? The inductance of the coil must be higher than the resistance of the coil, since the supply is providing 200*10 = 2000VA.
2000VA =sqrt[ (I^2 * R)^2 + (I^2 * L)^2]
4000000VA = I^4*R^2 + I^4*L^2
400 = R^2 + L^2
and 1000Watts = R*I^2, so R = 10 ohms
400 = 100 + L^2
L = 17.3 ohms
What are the advantages of instrument transformer?
'Instrument transformer' is the collective name for current transformers (CTs) and voltage (or 'potential') transformers (VTs/PTs). These transformers have two functions:
- to reduce the current or voltage in a high-voltage primary circuit to values that may be measured using regular ammeters or voltmeters ('burdens'), or to provide the current or voltage inputs to protection relays.
- to electrically-isolate their secondary burdens from the high-voltage primary circuit for the purpose of safety.
What are the condition of building up a self excited shunt generator?
self excited generator must be started without any external load attached ,an external load will continuously drain off the build up voltage and prevent the generator from reaching its proper operating voltage.
also the presence of residual magnetism plays an important role
And the field current resistance should be less than critic field circuit resistance
How do you transform transformers?
Open the equipment, unsolder the connections to the transformer, remove the fastenings and remove it. Order a new on on ebay, when it arrives unpack it carefully, place it in the equipment, fasten it in, and resolder the connections. Simple! - (Historikeren 13-07-2014)
Where is the friction on maglev train?
If you have two magnets they each have a north and south pole. The opposite poles will attract and the same poles will repel. Maglev trains create magnet fields on the track bed and the train of the same polarity. By controlling the generating of the fields you can hold up the train and propel it forward.
Since the train is not actually touching a track there is no appreciable friction except that caused by the surrounding air. In a vacuum you would have no friction.
What is the working principle of a DC shunt motor?
To ensure that the Lathe machine's motor working properly, DC motor starter is added in which it used to protect motor against damage from: • short-circuit, • long term overload, • excessive starting current, and yet to made the operating speed of motor easily to be control by operator. During starting, the motor is not turning, hence there is no internal voltage .The internal resistance is very low and thus the current flow through is very high. This condition may cause damage to the motor Hence, a staring resistor is added in which connect in series with the armature to limit the current flow until the internal voltage of motor is increasing to do the limiting. In order to prevent losses as the speed of the motor is build up; the starting resistor should be removed
What is the meaning of electrical components?
Electronic component are those component which are used to make the electronic circuit it may be active or passive .
some active components are - Diode ,FET,BJT,MOSFET, and HEMT etc.
while passive component are those device which can not process/amplify signal like- resistor capacitor inductor etc.
Light Emitting Diode (LED) & the Avalanche Diode. These are two types of diodes ,but there are more
