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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 will be Heat developed in current carrying carrying conductor?
Any conductor has resistance. Maybe not much, but there's always some.
Any resistance dissipates power, at the rate of I2R. (I = current through it, R = its resistance.)
That's how you build toasters.
What is the difference between positive and negative temperature coefficient of resistance?
Negative temperature coefficient of resistance means that as the temperature of a piece of wire or a strip of semiconducting material increases, the electrical resistance of that material decreases.
In a step up transformer how does the current drop if the voltage rises?
Transformers are rated in KVA, both the primary and secondary windings have the same KVA rating. (KVA is the voltage multiplied by the amperage then divided by 1000).
If you have a 10 KVA step up transformer with 120V on the primary:
A = 10k / 120 = 83.33A
and if the secondary produces 240V:
A = 10k / 240 = 41.667A
What is the difference between neutral and ground in a three phase system?
No matter whether we're describing a three-phase service or a a single phase service, the bare copper "earth" or "ground" wire normally carries no current. Its purpose is to provide an emergency path for current if ever there is any accidental contact between a hot wire and the external (or internal) metal parts of any electrical device which a user may be able to touch. The electrical device can be a motor, a water heater, an air conditioner unit or any other kind of appliance.
By carrying away the excess current in a fault condition - which should cause the protecting fuse to blow or the circuit breaker to trip - the "ground" or "earth" wire protects the building and its occupants because the power should be cut off before anyone gets electrocuted or any overloaded circuit wiring or appliances catch on fire.
The neutral is the normal "return" wire. In systems where the load is supplied from only one hot (or "live") wire, the neutral completes the circuit and carries current back from the load to the power station. In "Y-" or "star-connected" three-phase circuits the neutral doesn't normally carry any current if all three phases are properly balanced.
If the three phases actually have unbalanced loads - which can easily happen if each phase is being used to provide power to different single-phase circuits, each with their different loads - then some current will flow in the neutral wire and will result in unbalanced 3-phase currents flowing back to the power station.
All the neutral and ground (or "earth") wires in a building are tied or linked together at the incoming service main breaker panel. This is the only place they should ever be tied together because it is "upstream" of all the fuses and/or circuit breakers protecting the hot (or "live") wires for the various circuits installed in the building.
Warning: we must never assume that a neutral is safe to touch: it has to be checked with a voltmeter or a voltage indicator to be sure it is not "live". This is because a neutral wire is designed to carry current under normal circumstances.
So, if a neutral wire going back to the incoming main breaker panel has not been properly connected - or suffers a deliberate disconnection or some accidental damage which causes it to break - then it and any neutral wires connected to it further downstream will go live up to the break because of being connected to the downstream loads which still have hot feeds coming into them!
That is why we should never use a neutral as a substitute for a proper, separate, ground or "earth" wire.
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If some external accidental damage or electrical breakdown of the wiring's insulation occurred anywhere to the house wiring, to a socket outlet or to an appliance, these things could be very dangerous if there was no such protective wire.
For example, if there was no protective ground or earth wire, a fault could happen that is of a kind which did NOT draw enough extra current to blow a fuse or make the main circuit breakers on the incoming supply panel "trip" to cut the current off - but the wiring could still catch on fire and/or someone could be electrocuted!
Neutral wires are the return paths to the power generation station for current it supplies to the house or building via single live or "hot" wires in the branch circuits.
For more information please click on the Related Questions below.
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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
The effective resistance of three resistors, 120 ohm, 60 ohm, and 40 ohm, in parallel is 20 ohms.
RP = 1 / sum (1 / RN)
RP = 1 / (1 / 120 + 1 / 60 + 1 / 40)
RP = 20
The voltage applied, 120V, does not change the outcome. The power, however, of the three resistors is 120W, 240W, and 360W respectively. This is a lot of power, so please do not attempt to do it for real.
What happens to the energy of semiconductor when the temperature of the room increases?
When electrons are given energy, they can "jump" to a higher energy level or "electron shell". It would then be in an excited state. When it returns, it will emit the energy in the form of an electromagnetic wave (light).
A good example is a simple filament lightbulb. Electrons undergo thermal excitation (excited by heat) and will emit a whole range of electromagnetic waves (in the visable region of the spectrum, but also a lot of lower energy infra red light)
Conclusion about thevenin's theorem?
Thevenin's theorem is a basic equivalence principle for circuit design. It can simplify a very complex circuit to a very simple equivalent. This is done by finding the Thevenin Resistance as well as the Thevenin voltage and current. Once these are known, the equivalent circuit is simply a voltage source in series with a resistance.
Which is brighter series or parallel?
Parallel. Coz all the elements will get same voltages from the sources. in case of series connection, the voltage is divided between all elements.
A proportional controller is a type of a feed back controller where the difference between the measured output and the input (the desired output) is multiplied with a proportional gain and feed to the system.
40A*120V*5Hr = 24kW*Hr (Kilowatt-Hours)
CommentNo television would ever draw a current of 40 A!!!! Think about it, for a 120-V supply, that would make it have a power rating of 4800 W!!!!!! You would be able to use it for central heating!!!!
What are some of the benefits of a digital electricity meter?
A digital multimeter has the advantages of idiot-proofing and accuracy. The digital readout gives a single number instead of a dial pointing to several numbers on multiple scales.
How to calculate transformer core loss and iron loss?
there are several losses in a transformer that prevent it from attaining 100% efficiency. One is core loss, which can be divided into Hysteresis losses, Eddy currents and Magnetostriction loses. see for more details http://en.wikipedia.org/wiki/Transformer#Energy_losses
What happens to an electric current running along a wire?
In the case of a metal conductor, such as a wire, an electric current is the result of a drift of free electrons along the conductor. Free electrons are electrons that have become detached from the outer orbit of the metal atoms, and move haphazardly from atom to atom. You can think of these electrons behaving somewhat like a gas that fills the voids between individual fixed atoms. This 'gas' of electrons is in a constant state of rapid, random, and chaotic motion. However, when a potential difference is applied across the ends of the conductor, there is a tendency for individual electrons to gradually move from the negative end of the conductor to the positive end. Individual electrons move in this direction VERY slowly -in the order of millimetres per hour. Since this happens to ALL the free electrons at the same time, the effect of this drift is felt practically immediately along the entire length of the conductor.
Why tertiary windings in tranformer are often delta connected?
Transmission is always done in Delta - so only three conductors are required. However distribution may have to supply three-phase OR single-phase loads, so a neutral connection is needed. This requires a wye or star connection on the secondary.
How are voltage and current measured?
Electrical
Electrical current is measured with an ammeter and in units called amperes, or amps.
Stream Flow
River flow or current (discharge) is measured in cubic feet per second or cubic meters per second.
How kirchhoff laws will differ for AC circuit?
Kirchoff's Law is universally applicable, to AC as well as DC loops.
What is DC in electric stand for?
Volts direct current eg battery As opossd to Vac wich is volts altinating current eg mains supply
What will happen if a second bulb is added to a parallel circuit?
-- The voltage doesn't change.
-- If the second light bulb is identical to the first, then the total resistance drops by half.
-- If they're not identical, then we have to know the details of both before we can
calculate their combined effective resistance.
How can you change a 130v ac motor into a 110v ac?
To do it properly would require rewinding the motor with thicker wires in order to deal with the higher current caused by the higher voltage.
Difference betweeb Load balancing and Load sharing?
Load sharing is the ability to distribute outgoing traffic (or influence the flow of incoming traffic) over multiple paths. Load balancing is the ability to split the load toward the same destination (host or IP ) over multiple paths
>>.In regard to CISCO Routers:
Load sharing means one can split the traffic from a network to be transported by different routers (paths). That's exactly what Cisco does with MHSRP. The document on Configuring Multichassis Multilink PPP states that when it tells it to configure half of the hosts with one default gateway and the second half with the other. What happens, for instance, if the first half of the hosts are off? Will the traffic of the second half be transported by both routers?
On the other hand, load balancing means distributing the traffic evenly and dynamically among different paths to avoid link congestion and saturation. This can be done in a packet-by-packet basis or per destination in a round-robin fashion. The packets sent by a host follow different paths to the same destination. All paths belong to all hosts. And this is not what MHSRP does.
How electricity is transmitted to andaman?
No electricity is transmitted to Andaman from mainland.In fact it is generated at each island with the help of diesel generators according to need of the particular island.However, power is transmitted from Kalpong hydro electric project(North Andaman) to middle andamanwith transmission lines of 33 KV.
RFID tags use low, high, ultra-high and microwave frequencies. Each frequency has advantages and disadvantages that make them more suitable for some applications than for others. Countries will also have specific laws or regulations in place that prevent the use of certain frequencies.
Low-frequency: Operates from 30 KHz to 300 kHz, with typical operation being 125 kHz or 134 kHz. Advantages of LF are that they are going to be less subject to interference. Disadvantages of LF will be slow data transfer and the tags will must be read within three feet.
High-frequency: Operates from around 3 MHz to 30 MHz, and typically is used at 13.56 MHz. Advantages are that they have a slightly longer range than LF tags and have a faster data transmission. Disadvantages are that they will consume more power than LF tags.
Ultra-high-frequency: Operates from 300 MHz to 3 GHz and are usually found to operate in the 866 MHz to 960 MHz range. Advantages are that they will send information faster and farther than both LF and HF tags. Disadvantages are that their waves will not pass through items with high water content (including fruits and vegetables).
Microwave: Operate at 2.45 - 5.8 Ghz. Advantages are that they have very fast data transfer rates and can be read from much greater distances than LF, HF, and UHF tags. Disadvantages are high power consumption and high cost.
Note: Some persons refer to all tags operating above 415 MHz a Microwave tag
Can a ac motor produce electricity?
Technically YES. But the source of power in Electric cars being DC through batteries, the motor must be DC and not AC.
What are the readings for the experiment - to convert a galvanometer int ammeter?
A galvanometer is a type of ammeter an instrument for detecting and measuring electric current.
A galvanometer can be converted into ammeter by connecting resistance in parallel with it.
What Three types of windings are used on dc generator armature?
The winding of this type of transformer are made up of concentric coils. These coils are round, some being very small and other being larger, some have an open hole in the centre, making them shaped like a flattened donut, and some are solid. A few of the manufacturers have migrated into designing their concentric coils into a design which has caused them to be referred to as "spider coils" because the bracing of the coil's structure makes the overall appearance of the coil to resemble a spider's web.
