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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 are the uses of transistor in circuits?
Basically each and every amplifier circuit is made up of coupling or use of transistors.
The amplifier amplifies the signals because transistor makes either voltage or current to rise as a result of either of it's regions of operation i.e. open circuit(cut off region) or short circuit (saturation region)
Both the operation regions are not required continuously. Hecne the transistor works in either saturation or cut off regions only when emitter-base junction is forward biased, which can be applied as per requirement.
APPLICATIONS OF TRANSISTOR AND HENCE AMPLIFIERS ARE :
OSCILLATORS, LOUD-SPEAKERS, POWER AMPLIFIERS, VOLTAGE AMPLIFIERS, CURRENT AMPLIFIERS, ANALOG TO DIGITAL CONVERTER, DIGITAL TO ANALOG CONVERTERS
What Material Used For Electric Ovens using heating elements?
A resistor, which converts some electric energy to thermal energy!
Why wont a transformer function when supplied with direct current?
Transformers work on a principle called 'mutual induction' in which a changing current in one coil sets up a changing magnetic flux which links with a second coil, inducing a changing voltage into that second coil. I've emphasized the words 'changing' because its essential if mutual induction is to take place. Alternating current is a type of current that is constantly changing in value and direction, whereas direct current is a constant current -so transformers require a.c. to operate.
Why earthing transformer is zigzag connection?
A zigzag transformer is used in connection with 3 phase and is made up of 6 coils connected in a "Y" manner. Each leg of the "Y" is made up of a coil on a different phase leg of the transformer. The neutral formed by the zigzag connection is very stable. Therefore, this type of transformer, or in some cases an auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer, lends itself very well for establishing a neutral for an ungrounded 3 phase system. Many times this type of transformer or auto transformer will carry a fairly large rating, yet physically be relatively small. This particularly applies in connection with grounding applications. The reason for this small size in relation to the nameplate KVA rating is due to the fact that many types of grounding auto transformers are rated for 2 seconds. This is based on the time to operate an overcurrent protection device such as a breaker. Zigzag transformers used to be employed to enable size reductions in drive motor systems due to the stable wave form they present. Other means are now more common, such as 6 phase star.
How do you selecte cable for load?
if your load draws a max of 15 amps then you would use 14-16 gauge wire. the lower the gauge the more current that is allowed to pass. there are charts that show max current for diameter of wire
How are step up transformers used in the transmission of electric energy?
Step-up Transformers used in the transmission of electrical energy increase the voltage going over Transmission Lines (over 100,000 Volts). For a given amount of POWER to be Transmitted, the higher the Voltage, the LOWER the CURRENT. This reduces the amount of Power LOST to the Resistance of the Transmission Lines.
Power Lost is calculated by the Formula:
POWER Lost = I2 x R, where I=Current and R=Resistance
So, the lower the Current (I), the lower the transmission line losses.
At the end of the Transmission Path the Voltage is "Stepped Down" to a value usable for the Customer, usually (220 volts for Residential use in the USA).
A transformer's capacity is rated in volt amperes(V.A). This is the product of the secondary winding's current rating and voltage rating.
Which type of magnet use in maglev train?
The carriages are made of wood and metal. The motor is a series of electro-magnets.
Your question should read, "How many kW.h are there in 0.07 GW.h?" It's important to use the correct symbols.
There are 1000 000 000 kilowatt hours in one gigawatt hour -so you can now work it out for yourself.
Why are metals thermally conductive?
Because metals are the good conductors of current. the conduction band and the valance band are overlap on each other,so when the current passes from the metal because of overlapping on both the bands current passes easily.
How much step down transformer cost?
Your question is rather like asking, "How much does a vehicle cost?" Is the vehicle a bicycle or a jumbo jet? So, the answer to your question depends on (a) what you mean by a 'power transformer' (there are various definitions)?, (b) what are its power and voltage ratings?, (c) is it single phase or three phase?, and (d) are you including the cost of its cooling system?
Will 12 volt 2000mA transformer work instead of 12 volt 2500mA transformer?
I think you mean a d.c. power supply, not a transformer which is an a.c. device. The rule is that the power supply's voltage must match that of the load, but its current rating must exceed that of the load. So it is perfectly fine for a 12-V 2.5 A power supply to be used with a 12-V, 1000-mA load (it is the load that determines the current drawn from the power supply).
Why armature winding resistance is less than field winding resistance?
An 'armature winding' is the rotor winding, and the 'field winding' is the stator winding.
Transformers works on the Principle of?
If you mean how they work then magnetic fields
Induction. Voltage applied to one winding induces a voltage in another winding. The voltage induced is dependent upon the turns ratio between the two windings.
Current is said to be induced in the other winding as well (since a voltage is induced, current will flow if the circuit is complete). Depending on the transformer type, current may flow directly from the series winding (in autotransformers, for example) to the secondary output (conduction, as opposed to induction).
Can a motor supply electricity?
For some kinds of electric motors - not all kinds - the answer is yes.
It is hard to explain the reasons using very simple terms, but here goes:
Most small direct current electric motors that have stators which are made of permanent magnets can be made to generate direct current electricity when their rotors are turned at a fast enough speed by another engine, such as, for example, a car engine or a steam engine.
For more information see the answer to the Related Question shown below.
To answer these questions I will tell you which devices or equipments are inductive.
These include:
- Transformers
- Hair clipers,hair blowers,
- motors
You hopefully know what those devices or equipments are used for,hence why we use inductors.
What is meant by power factor?
The cosine of phase difference between the voltage and current...........
Power factor is actually the ratio of the electrical 'true power' that does work in the real world - the 'watts' of power that are converted to mechanical motion, heat etc - compared to the 'apparent power' volt-amps that the meters on the panel seem to show the load as using.
Circuits containing inductors or capacitors draw energy from the supply mains to 'charge' (ie, store energy in their magnetic or electrostatic fields) while the voltage of the sinewave is changing but they return this energy to the supply 90 degrees later. This means they are drawing a current (drawing volt-amps), but not doing useful work with that current, so they're not consuming any true power (watts). An effect of inductors and capacitors is that they move the current waveform out of phase with the voltage waveform. The higher the proportion of stored energy to useful work, the greater the angle between voltage and current.
Pure resistors don't store any energy, so all the volt-amps they draw get used as watts in the load. There's no phase shift between voltage and current, so they're 'in phase'. All the volt-amps are used as watts, so true power equals apparent power, and the ratio of true power to apparent power is 1.0 in a resistor. It has a 'power factor' of 1.0, or 'unity'.
Circuits with inductors (or capacitors), though, draw volt-amps, some of which do useful work (eg, an inductive motor drives a load and heats the cooling air) and some of which is returned to the mains (from the stored magnetic field in the motor windings collapsing). Because some of the volt-amps are returned to the mains, there's less true power than volt-amps - so the power factor is less than 1.0 F'rinstance, a 220 volt motor draws 10 amps at full load, but delivers 2000 watts of power at the same time. It has a power factor of (true power) / (apparent power) = 2000 / (220 x 10) = 0.91
That means 91% of the 'apparent power' - volt-amps - is actually doing useful work - true power. Some places give power factor as a decimal fraction - 0.91 - while others give it as a percentage - 91%. In all cases, though, the angle between the voltage and the current - the 'phase angle' - can be found by finding the angle that has a cosine equal to the power factor. eg, the phase angle in the above example is (cos-1(0.91) or about 24.5 degrees lagging. That's what the answer at the top of this question is saying.
Advantages of intermediate frequency?
The intermediate frequency, or IF, in a superhetrodyne receiver is used to tune the desired signal.
The IF stage is tuned to a specific, fixed frequency, usually 455 kHz for AM and 10.7 MHz for FM. Since the IF stage does not need to be adjustable, it can be designed for high performance, tight bandpass operation.
This is far easier to do than creating an adjustable RF stage with tight bandpass operation. Instead, the RF stage is broadband and the IF stage is narrow band.
The actual tuning of the receiver is done by varying the local oscillator that is mixed with the radio frequency (RF) signal just upstream of the IF stage. The difference frequency of the output of the mixer is then amplified by the IF stage.
The audio information, to be fed to an amplifier and be heard on the speaker, is extracted after the last IF stage - either by a detector in AM or discriminator in FM.
What is a line to line voltage?
In a 3 phase system, the voltage measured between any two phase is called line to line voltage.
And the voltage measured between line to neutral is called phase to neutral (line to neutral) voltage.
AnswerThere is no such thing as a 'phase-to-phase' or a 'phase-to-neutral' voltage. The correct terms are 'line-to-line' and 'line-to-neutral'.
The voltage between any two line conductors is called a line voltage.
In a three-phase, three-wire, system, the line voltage is numerically equal to the phase voltage.
In a three-phase, four-wire, system, the voltage between any line conductor and the neutral conductor is called a phase voltage. The line voltage is 1.732 times larger than the phase voltage.
Why is three-phase alternating current used for distribution systems?
Simply because it is cheaper. (You dont need the extra wire)
However you can only use a 3 wire system if the load is a balanced load. If the load is not balanced you need the fourth wire (neutral/return) to take the out of balance current.
How many KW is required to run 40 hp 3 phase motor?
W (Watts) refers to the resistive (real) power of an appliance. Providing that the circuit is purely resistive then 60kW = 60kVA, if the appliance circuit includes capacitance / inductance more information is needed to answer the question such as the power factor or phase bewtween voltage and current. Assuming a house supply of 240 V (rms), 60kVA would represent a current of 60k/240 = 250 Amps. Note that a single house ring mains fuse/trip is usually 60 Amps.
Does aluminum conduct cold faster than glass?
Aluminum is a conductor and glass is an insulator.
Conductors allow the flow of energy transfer, but insulators block this transfer of energy. So by definition, Yes, aluminum conducts cold or heat(energy) transfer faster than glass.
