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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 a phase discriminator?
A Phase discriminator allows the user to shift in time or 'phase' into another dimension. It shifts the user into another dimensional phase which can be a fraction of a second off from our own, which renders the user invisible to those in the normal unshifted time frame.
How can you use a 3 phase capacitor as a single phase capacitor?
Just use any two of the three terminals that are available, this will give you a single phase capacitor.
What is positive isolation in plant?
Positive isolation is a method of Isolation where there is Zero potential of energy at the workplace.
- All Hazardous Energy has been identified
- All are isolated at the source
- Residual Energy has been eliminated.
eg. Electrically Isolated at the Transformer, earth applied, and fuses removed.
eg. Mechanically Isolated at the Pump, valve closed, blanked-off. Line drained, purged, etc
While one might expect a latin symbol for amperes or milliamps, A and mA are the accepted symbols for these.
How does electromagnetic induction works?
Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field. Basically it works because of electricity.
100w bulb and 60w bulb connected in parallel to 220v which will glow brightly?
Total supply voltage = 220v
rated power of first lamp= 100 watt
so current though it, I=p/v
I=100/220=.45 amps
Resistance offered by first lamp=220/.45= 488 ohms( i avoid fractions)
..............................................................
rated power of second lamp=60 watts
voltage is same, so current through it = 60/220=.27 amps
resistance of second lamp = 220/.27=814 ohms( i avoid fractions)
.........................................................................
power drawn by first lamp =I12 R
=(.45)2 * 488 =98.82(=100)
power drawn by second lamp =I22 R
=(.27)2 * 814 =59(=60)
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SO 100 WATT BULB WILL GROW BRIGHTER AS IT HAS MORE POWER
What are No Load And Locked Rotor tests on a three phase induction motor?
Doing a No Load test of a 3-phase induction motor involves the measuring of current, voltage, torque etc with no load on the rotor shaft, meaning that it is free to turn but is not driving anything else.
Similarly a Locked Rotor test involves the measuring of current, voltage, torque etc with the rotor shaft "locked" i.e. prevented from turning, which is the worst loading condition the motor would ever have to contend with.
What are the advanced applications of DC series motors?
what are the advanced applications of dc series motor
Experimental error caused by instrumental limitations?
Error caused by instrumental limitations is actually called systematic error, not experimental error.
What is the total resistance of a circuit that contains two 100 resistors connected in paralle?
50 ohms
What is the power of a parallel circuit with a resistance of 1000 ohms and a current of 0.03 amps?
.9 watts.
Can resistors function the same in AC circuits as in DC circuits?
Yes, they both can add a load to a circuit.
When use undervoltage release?
Under voltage protection (release?) is used in industry. If there was a power failure and a piece of equipment was running when the failure occurred for safety reasons the machinery should not start up on its own when the power returns back on. With under voltage protection the operator restarts the machinery after checking that there is no danger to anyone and the machine is clear to start. To obtain this safety feature an electrical contactor is used in conjunction with remote stop - start buttons located at the machine the operator is working.
A tap changer is a device on the outside of transformers to allow the changing of the primary windings to except different primary voltages. A common one is 7200 - 14400 volts. Look up at the transformers on the poles to your house and you will be able to see this handle with the voltages stamped on the case and the handle in one of the positions. This allows for the transformer to be used on two different primary voltages. What this cuts down on is storage of single primary voltage transformers.
CommentTap changers are normally incorporated into the high-voltage, rather than the primary, winding of a transformer.
What is quadrature axis reactance?
If the stator winding of a synchronized machine, which consists of many coils that are basically connected as a series
circuit, is not connected to a load then the resulting emf from all the coils is the open circuit emf of
the phase winding. Closing the circuit on to a load causes a steady state current to flow in the stator
coils. Each coil creates a flux and their total flux opposes the field flux from the rotor. The resulting
flux in the air gap is reduced. The emf corresponding to the air-gap flux drives the stator current
through the leakage reactance and conductor resistance of the stator coils. The voltage dropped across
this winding impedance is small in relation to the air-gap voltage. Deducting this voltage drop from
the air-gap voltage gives the terminal voltage of the loaded generator. In the circumstance described
thus far the reduction in air-gap flux is called armature reaction and the resulting flux is much smaller
than its value when the stator is open circuit. Restoring air gap and terminal voltage requires the
field current to be increased, which is the necessary function of the automatic voltage regulator and
the exciter.
When the rotor pole axis coincides with the axis of the stator coils the magnetic circuit
seen by the stator has minimum reluctance. The reactance corresponding to the armature reaction
in this rotor position is called the 'direct axis synchronous reactance Xsd '. If the stator winding
leakage reactance, Xa, is deducted from Xsd the resulting reactance is called the 'direct axis
reactance Xd '.
A similar situation occurs when the rotor pole axis is at right angles to the axis of the stator
coils. Here the magnetic reluctance is at its maximum value due to the widest part of the air gap facing
the stator coils. The complete reactance in this position is called the 'quadrature axis synchronous
reactance Xsq '. Deducting Xa results in the 'quadrature axis reactance Xq '.
Does the impedance of a parallel RLC circuit equal to the value of the resistor?
No. You have to consider the inductor and the capacitor.
Impedance of RLC circuit is equal to to the Value of Resistor Only AND Only on Resonate frequency.
otherwise u have to cnsider resistance inductance and capacitance together in series.
What is commutation in DC machines?
It is the process of conversion of generated ac voltage into the armature of a dc generator to dc voltage at the terminal of the dc generator by use of pair of brushes and commutator.
OR It is the process of conversion of given dc voltage at the terminal of the dc motor to ac voltage in the armature windings in a dc motor by use of pair of brushes and commutator.
