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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
In a series circuit which quantity remains same throughout the circuit?
Current flow remains the same throughout the circuit.
What is the function of an electric motor in terms of electric power and motor?
The electric motor changes electric energy into mechanical energy.
12 Amperes is.
Why speed of the induction motor falls when load is increased?
As the load increases, the speed reduces to deliver the increased torque required.
Can a 415volt 3phase motor run on 525 volt 3 phase?
It is not advisable to run lower voltage motor on a higher voltage.
Removing any bulb breaks the continuity of a series circuit, stopping the flow of electrical current. Removing a bulb in a parallel circuit does not interrupt the current flow, so the remaining lights continue to conduct electrical current.
What happens in the winding house of a mine ?
The winding house houses the engine that raises and lowers the mine's cage (lift).
A volt ampere (symbol: V.A) is the unit of measurement for the apparent power of a load connected to an AC supply. Apparent power is the product of the supply voltage and the load current. Apparent power is the vector sum of a load's true power (measured in watts) and reactive power(measured in reactive volt amperes). '15 kV.A', means 15 000 V.A.
Further explanation
In the descriptive name "kVA", k = 1000 and VA = volt.amperes.
Volts x amps = volt.amperes, for which there is an international standard unit named the watt.
Therefore 15 kVA is 15 000 volt.amperes which, for a purely resistive load, can also be stated as 15 kilowatts.
If the distribution voltage and type is known, you can then calculate the current in amps that will flow at that power rating if the load is purely resistive i.e. if the power factor is 1.
If the power factor (pf) is less than 1 then, because
watts = volts x amps x pf
then, at a given service voltage, more current must flow to produce the same apparent power as you would get with a purely resistive load.
Answers.com says it is a microwave amplifier in which a Gunn oscillator functions as a negative-resistance amplifier when placed across the terminals of a microwave source.
A comparator(electronic such as an LM393*) works by sampling two input pins and turns on an output when there is ether a difference or similarity of the inputs.
it depends on how the comparator is used int he design.
Say you have a reference voltage on the "inverting"( - ) pin of 5 volts.
And you have the "non-inverting" ( + ) connected to measure a voltage.
when the voltage on the Non-inverting side equals the inverting voltage. the Output
pin will turn on. Usually the Output Pin is open and will switch to ground once the comparator is activated. Remember since most all comparators have open-collector outputs, you will need the pull-up the pin to the source voltage through a resistor to see the switching action.
To make the put act differently, (instead of switching to ground when active) all you need to do is exchange(swap) the input pins.
See www.national.con for a datasheet on the LM393
What kinds of circuits need precise resistors?
Timing circuits, and any circuit that depends on the resistor value being fairly precise, such as voltage dividers and comparators. Old story....engineers knew that you couldn't pick through a bunch of loose precision resistors to find close tolerance resistors....The manufacurer already took the close precision resistors and sold them separately. This is not so true these days. Even low tolerance resistors might be high precision. Usually the manufacturer will fill the loose precision needs with parts better than required.
If it is a computer power supply it is the box that gives the computer its power from the outlet.
How are substations protected?
Almost all of the equipment inside of a substation is used for the purpose of protection.
The circuit breakers and power transformers in the substation are equipped with current transformers (CTs) that step down the current passing through the equipment to a level that can be read by protective relays. These protective relays can cause the breakers to trip upon many different events including under/overvoltage, current spikes, frequency issues, transformer/bus differential, etc.
The breakers in a substation are placed strategically so that different pieces of equipment or sections of a circuit can be isolated without loss of service to the customer.
For very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customised solutions; for example, aircraft flight controls.
* Manufacturing Industry
- Lead acid battery plant, complete manufacturing system
- Extruder factory, silo feeding control system * Travel Industry
- Escalator operation, monitored safety control system
- Lift operation, monitored safety control system * Aerospace
- Water tank quenching system * Printing Industry
- Offset web press print register control system
- Multi stage screen washing system * Food Industry
- Filling machine control system
- Main factory feed water pump duty changeover system * Textile Industry
- Indutrial batch washing machine control system
- Closed loop textile shrinkage system * Hospitals
- Coal fired boiler fan change-over system * Film Industry
- Servo axis controlled camera positioning system * Corrugating
- Main corrugator machine control system
- BOBST platten press drive and control system * Plastics Industry
- Extruder factory, silo feeding control system
- Injection moulding control system * Agriculture
- Glasshouse heating, ventilation & watering system * Foundry
- Overhead transportation system from casting process to shotblasting machine * Leisure
- Roller coaster ride and effects control system
- Greyhound track 'Rabbit' drive system
Why should the input resistance of a instrumentation amplifier be as high as possible?
Comment: If you are not sure about your facts, I see little point in offering an answer.
AnswerConnecting an amplifier to a transducer/sensor inevitably changes the conditions of the phenomena being measured. This is due, primarily, to the amplifier drawing, an albeit small, current from the transducer.The higher the amplfier's input impedance, the lower the current drawn, and hence the less the disturbance to the original conditions.
How do you determine a resistor's wattage?
The physical size of the resistor determines how much power(wattage), or heat can be dissipated. The larger the resistor the more power it can dissipate. Resistance is the opposition to current flow(electrons) and this opposition causes heat to be generated when current flows through it.
The AMOUNT of Heat dissipated per unit of time is measured in watts.
example if P=I X E (power formula)
P=Power(watts)
E=Voltage
I=Current
ohm's law-->E=I X R
say you are using a 1/2 w 100 ohm resistor and you put 12VDC thru the resistor to ground.
determine the current: I=E/R
I=12V/100 ohms
I=120 ma.
Plug in value into ohms law formula.
P=I X E
P=.120 x 12
P=1.44 watts (resistor will be dissipating 1.44 watts at 12v with 120 milli amps flowing thru it.
Resistors come in different wattage values( 1/8w, 1/4w, 1/2w, 1w etc) usually printed on them. So for this case you would need at least a 2 WATT resistor and still be safe and NOT BURN and destroy it to a crisp.
If the resistance has not changed then your resistor passed the required safe amount of current.
If the resistance has changed you may have burned the resistor with too much current and thus you have overpowered it.
You can also use a wattmeter and measure the wattage as voltage and current is applied to the resistor at a given resistance.
Basically the movement of the speaker is the cause of the stereo (mono speakers) making the noise via induction. The Induction is the result of controlled oscillation of electrical current.
A speaker is essentially an air pump. I like to say the bigger the pump the bigger the sound!!!
A driver is a device that reproduces sound. Drivers consist of woofers, subwoofers, tweeters, midranges, compression horns etc. A driver consists of a magnet assembly, a metal or composite basket/frame, coil and cone or dome.
A driver has a coil of wire that is electrically attached to your amplifier. The coil is the electro magnet not the magnet itself. The magnet is usually made of ceramic but used to be made of Alnico (Aluminum, Nickel, Cobalt; expensive compared to ceramic) and is more often now made of neodymium (a lighter stronger material than ceramic). The magnet has a permanent magnetic polarity that does not change. When the coil of wire is placed inside the magnet assembly "pole piece" and an alternating signal is placed thru the coil it will cause the coil to oscillate as the coil will now attract and repel within the magnet assembly as the polarity changes on the coil. The coil is attached to a cone (or dome in the case of tweeters and some midranges) which is capable of moving air more effectively.
Speakers consist of these drivers usually a woofer, a tweeter, and sometimes a midrange. A speaker will almost always also have a crossover network which is basically a filter network that effectively divides the signals to each driver so that the bass only goes to the woofers and the high freq only goes to the tweeters.
Typical speaker arrangements contain multiple speakers: two for a simple stereo system, or more for more recent systems. All multi-speaker systems need observing the polarity such that the coils in all speakers make the same, synchronized, movement: in a multi-speaker system, some sounds only come out of the left speaker, or the right speaker. That makes the stereo effect. The majority of the sound, however, is being emmitted through all speakers at the same time. The bass drum, for example, can typically be heard through the left and the right speaker at the same time.
Wiring all the speakers in such a system while observing their polarity allows the speakers to make a syncronized movement. For example, when the bass drum hits, all affected speaker coils would make a movememt towards you, then away from you, etc. If one of the speakers is wired with the reverse polarity, this speaker would start by moving away from you, then towards you. Air would simply be shifted back and forth between the speakers, instead of applying pressure on your ear drums.
To avoid that effect of lost sound energy, speakers should be wired up with the same polarity even though they are driven by an alternating current (AC) signal.
Additional
Another type of speaker is the electrostatic loudspeaker. Electrostatic loudspeakers are generally very much more expensive than the electromagnetic loudspeaker described above and, in most cases, far superior. Physically, they look completely different from conventional loudspeakers, usually taller and wider, but very much thinner (rather like a plasma television compared to a CRT television!).
Electrostatic loudspeakers work on the principle of attraction and repulsion between electric charges. The general principle is as follows. The diaphragm ('driver') , a large rectangular flexible sheet of material, such as mylar, is coated with a conducting layer and placed between two large metallic perforated sheets. A high DC voltage is placed between across this arrangement and the audio signal is impressed upon the voltage, causing the polarities to change in magnitude and direction in accordance with the musical signal. The result is that the flexible sheet will then move, acting in much the same way as the diaphragm described in the previous answer. Compared with electromagnetic loudspeakers, the diaphragm is much lighter and reacts far more rapidly to variations in signal. Furthermore, because the whole of the surface of the diaphragm is charged, the resulting forces are applied to the whole of the surface of the diaphragm rather than being 'pushed' or 'pulled' by a separate coil -as is the case with the magnetic loudspeaker.
Like electromagnetic loudspeakers, electrostatic loudspeakers also have 'woofers' and 'tweeters' -different-sized rectangular diaphragms.
Because electrostatic loudspeakers require a very high voltage (thousands of volts) to operate, they each have a heavy built-in transformer and rectification system and must, therefore, be connected to an electricity supply.
Electrostatic loudspeakers were developed, commercially, by a British hi-fi company called Quad, which has been manufacturing them since the 1950s.
What is the voltage and amp service at the street before it steps down to the residence?
The voltage and ampacity can vary depending on the demand of the neighborhood. The voltage is typicaly 240 volt with the amperage capacity varying. 7,200 volts goes to the transformer on the pole, amperage varies.
Why there is no starting torque for synchronous motor?
The 3 phase supply is provided in the stator of a synchronous motor which produces a rotating magnetic field.The stator has field poles(North and south). Now due to the rotating magnetic field the current is induced in the rotor of the motor as due to ampere's law, so the motor tends to move.Now as the stator poles induces opposite poles on the rotor, after moving the first pole pitch the rotor gets repelled by the opposite stator poles and due to the heavy inertia of the rotor it can't respond and the motor is standstill.Hence the synchronous motor is started with the help of an auxiliary motor or such called a pony motor to overcome this problem.
Ohm's Law: V = IR (voltage = current times resistance).
Ohm's Law: V = IR (voltage = current times resistance).
Ohm's Law: V = IR (voltage = current times resistance).
Ohm's Law: V = IR (voltage = current times resistance).
What is earthing of electric motor?
This is avoided by grounding the motor frame. Both methods effectively produce a solid electrical connection straight to the stator laminations, allowing any insulation failure to be grounded via the end-ground user's conductor. Earthing is a technique in preventing electric shocks. To start, virtually all electric motors require grounding. The neutral earthing is given in the generator, transformer, motor, and other electrical devices by connecting the non-current carrying section to the neutral earthing.
