0
Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
How many amps for a 200 kva 3 phase generator working on 240 V per phase?
KVA means product of voltage and current. For 3 phase generator, its KVA = (1.732 X (Line Voltage) X Current)/1000.Put line voltage in this equation and get current.
Can you use a 9 V DC transformer to power a 3 V DC motor?
No, not unless there is a 115-volt power inverter to convert the 12 VDC to AC at the higher voltage. There are inexpensive inverters available to plug into a cigarette lighter outlet in a 12V vehicle system, but only for up to about 150 watts.
What causes three phase induction motor fails to start?
One possable reason for failure to start could be as simple as a brush not making contactwith the commutator. Also if the commutator segments are dirty this could also contribute to the problem
What does it mean to source current?
the source current is the current that flows from the power source.
What is the color of wire used in an isolated ground system?
All ground wires are green or green yellow marker.
Why is a three phase induction motor self starting?
A brushless DC motor is self-starting using only one magneto-sensitive element because the motor is of a two-phase type and is provided with a detection device which detects towards which of the two phases the rotor is mainly directed. A presetting circuit compares the detected rotor position with the state of an energizing circuit in order to set this circuit so that the energizing circuit energizes the stator phases for said specific rotor position in such a way that starting of the motor is guaranteed, although initially with an undefined direction of rotation. By presetting the commutating direction of the energizing circuit the rotor subsequently locks onto the field and rotates in the correct direction if it has started in the incorrect direction
An ammeter is a low voltage voltmeter in parallel with a small resistance resistor. Current flow through the resistor creates a voltage drop across it which is then measured by the voltmeter.
What is the real power if E rms is 100V current rms is 2A and the circuit has a power factor of 0.8?
solution: Erms=100 V Irms=2 A p.f.=0.8 As per formula, Power(W)= Erms * Irms * p.f. = 100 * 2 * 0.8 = 160 W The ratio of watts average power (the average power measured in watts) to the apparent power of an alternating-current circuit. By definition, the equation below holds, which is the ratio of instrument readings. A watt-meter indicates average power, and http://www.answers.com/topic/electrodynamic-instrument or iron-vane instruments show rms voltage and current. For the steady-state ac circuit under sinusoidal voltage and current, pf = cos θ, where θ is the phase angle between the voltage and current. This definition is restricted to sine waves of the same frequency.
What is the continuous flow of charge in a circuit?
Most people say electrons (which are negatively charged). Some who are really out there might say it's a flow of holes moving the other direction.
What are the major responsibilities of an electrical engineer?
well obviously to facilitate electrical facilities
How does the changing the battery voltage affect the current?
If voltage varies then current varies with constant resistance.
An N.C. contact is 'Normally closed'. This applies to relays (electronic switches). You can use either a normally closedcontact or a normally open contact to do what you need, provided the relay has both and depending on your situation. Here's a recent example of mine: A building's fire alarm is wired to the HVAC system to shut down ventilation in case of a fire. In this case we want the HVAC to have power normally but remove power (with the relay) during a fire alarm. We would connect the HVAC power to the relay's N.C. (normally closed) contacts, because they are exactly that: normally closed. This would allow the HVAC to function. When power is applied to the relay, it would switch contacts, disconnecting power to the HVAC. An important note is that contacts and other electrical connections that can change condition (such as a relay) are described in a de-energizedstate. Thus, the N.C. contacts are normally closed, while the power to the relay is off. Likewise, a N.O. contact is open with relay de-energized but will close upon supplying power to the relay.
Why is RF amplification needed in a radio receiver?
In a typical radio receiver, there will be, a tuning stage, several IF stages, followed by an audio amplifier. (And a few other ancillary bits we'll ignore here.)
The signal from the aerial could be a microvolt or less, and the voltage required at the audio stage will be a few volts. It is not absolutely essential that any of the amplification take place in the tuning stage. Most of the amplification will take place in the Intermediate Frequency stages, and a little more in the audio stages.
Is 480VAC aplliances three phase?
Not necessarily, in the UK in the 1950s and 60s there were single-phase 480 V supplies with a neutral centre-tap giving two 240 V supplies with opposite phase. It is still used in rural areas, a three-wire single-phase supply, but individual properties do not normally have a 480 V supply.
Normally the supply is used for small groups of houses where half the houses are put on one side of the supply and the others on the other half. When both groups of houses use the same amount of current, there is no current returning in the neutral wire, which gives lower distribution losses.
What happens if the direction of current at the terminals of a series motor is reversed?
No changes will occur by wiring a 110 volt motor in reverse polarity, rotation will always be the same. Some single phase motors are designed to be reversed ,but that is a function of the relationship of start windings and capacitors and requires some wiring changes in a motor junction box or an end terminal housing, not by just changing the incoming power.
A rheostat is a resistor with variable resistance.There are many type of rheostat,involved of a rotary-type rheostat and a sliding rheostst.I dunn know much about the rotary-type rheostat but I can tell u how does a sliding rheostat work.
A sliding rheostst consists of a coil resistance wire wound on a tube and a sliding contact.The sliding contact be moved on the metal bar.Consider of the length of the resistance wire which let electric current through increases,the reistance would be higher and decrease the elctric current.Thus by moving the sliding contact,we can adjust the size of electric current.It's ofter used as a dimmer or to adjustl the voluime of the radio.
If you are interested in the rotary-type rheostat,try to find it by yourself!
What is a sinusoidal wave?
This is a wave that appears to have curves. AC current/voltage. If you see a wave on a ossiloscope of what our AC (Alternating current) mains voltage that will be the answer to the question. DC (direct current) does not appear to have the same qualitys
How could you test the circuit before you power it up?
There are many ways of testing many types of circuits. The procedure depends on the circuit. It is important though not to play with electricity unless you know what you are doing yourself properly. If you don't know, take the circuit to someone who does. DO NOT PLAY AROUND WITH ELECTRICITY WITHOUT SUPERVISION. DO NOT PLAY WITH MAINS OPERATED EQUIPMENT UNTIL YOU HAVE AT LEAST COMPLETED A COURSE. DO NOT USE WATER BASED FIRE EXTINGUISHERS ON ELECTRICAL FIRES. NOBODY AT WIKIANSWERS WANTS TO SEE YOU HURT.
Why is a section of the battery referred to as a lead-acid cell?
Alkaline batteries are named for their highly alkaline electrolyte solution which is potassium hydroxide (aka caustic potash, aka "traditional" lye) mixed with water.
Lead-Acid batteries are similarly named in-part after their highly acidic electrolyte solution consisting of 35% sulfuric acid and 65% water.
How do you know if a capacitor is good or not?
You test it.
For electrolytic capacitors, it's sometimes (but not always) obvious simply by looking at it that there is a problem; if the capacitor bulges or is actually ruptured, that's a pretty good indication that it might be bad. However, the only way to know for certain is to check it to see if it has the proper capacitance.
For various reasons it's difficult to test the capacitance of a capacitor which is in a circuit; you'll usually need to detach it and test it in isolation. It is possible to check the equivalent series resistance of a capacitor without removing it from the circuit, and in some cases this may be enough (a correct ESR doesn't necessarily mean the capacitor is good, but an incorrect one means that it's bad).
What is the advantage of using the centre tapped full wave rectifier?
By using a center tap, with the tap connected to ground you can use one winding for the positive AC swing and the other winding (both relative to the center-tap) for the negative swing. Thus, when the secondary windings can be connected to the AC inputs of a full-wave-bridge rectifier to harvest a bi-polar DC power source.
i.e. - a positive DC voltage 'rail' AND a negative DC voltage rail, say for example you have a 24VAC center tapped secondary of a 110VAC transformer. With a full-wave bridge, the center tap becomes the circuit 'ground' (aka 'return') in a DC circuit.
How much does it cost to build a water turbine?
A small home use Hydroelectric turbine costs about 5,000 if you want a good turbine and 2,500 dollars if you want a cheap but not efficient turbine.
What are the advantages of kelvin double bridge over wheatstone bridge?
1) a bridge based on the principle of Wheat stone's bridge that is
used to compare two nearly equal resistances and to determine values of low resistances
and the specific resistance of a wire. It differs from a meter bridge because additional
resistances of similar magnitudes are included at either end of the meter wire.
