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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
Difference between relay and solid state relay?
All solid state relays are relays, but not all relays are solid state relays.
There are three basic kinds of (protective) relays I know of: electromechanical (rely on induced voltages and currents to spin disks or energize solenoids), solid state (built with solid state parts - basically prerequisites to microprocessors), and microprocessor based relays (fancy computers).
What is the value of power factor for a pure inductor?
Angle between v and i is 90 deg
so, cos 90 = 0
Same for pure capacitor
Why is current the same in all points of a circuit even with resistors on it?
Electrical current (amperes, or coulombs per second) is the flow of electrons from one point to another. In a series circuit, there is only one path for those electrons to flow, so the amount of flow at different points in a series circuit is always the same.
That's not to say that the current does not change - certainly different resistance, for instance, would cause different current - the point here is that, for a given set of conditions, the current in a series circuit is the same at every point in the circuit.
This is Kirchoff's current law. The signed sum of the currents entering a node must always be equal to zero. If a node consists only of two elements, then the current entering the node from one element must be equal to the current leaving into the other element. Since a series circuit consists only of nodes with two elements connected together, that means the current at every point in a series circuit is the same.
Think of this analogy. Connect several water hoses in series with modulating valves between each section. Apply water pressure to one end. Make different adjustments to the valves, representing different resistances. Note that, although the water pressure is different at different points (think voltage), the current flow at different points (think current) is the same.
Explain the operation of jfet with any time?
Figure 118: n-channel JFET structure.
When , there is little voltage drop along the length of the channel, and the depletion regions are parallel, Figure 119. As vGS is increased negatively, they eventually touch reducing iD to zero. The value of vGSat which this occurs is called the pinch-off voltage, Vp (or vGS(off)).
Figure: n-channel JFET structure for showing parallel depletion regions.
When , there is a voltage drop along the length of the channel, and the depletion regions are no longer parallel, but are closer together towards the drain, Figure 120. As vDS is increased, they will touch (pinch-off) towards the drain, and the drain current iD can increase no longer. At the threshold of pinch-off, vGS-vDS=Vp. As vDS is further increased, iD remains constant, and the JFET is in its current saturationregion, the normal mode of operation. (This constant current region is a characteristic feature of any transistor, FET or BJT.) The channel shape remains unchanged, with a small region of touch near the drain, and further increases in vDS occurs across this small region.
Figure: n-channel JFET structure for showing non-parallel depletion regions.
JFETS are high input impedance devices, and so (due to the reverse bias pn junctions).
The "pick up" of a relay is a setting at which the relay will begin to operate. Such as an overcurrent relay - if the pickup is set to 5A, when 5A is flowing through the relay, the relay will operate.
Why does the coil have to spin in a generator?
A coil has to spin in a generator to produce electricity.
Why frequency remains constant in transformer?
First we know that transformer is a statical electrical device that transfer electrical energy from one circuit to another circuit with out change its frequency .....it may be voltage or current is change simultaneosuly or separately .... and point is why does not change the frequency in the transformer because the there is no moving part in transformer....As we know that frequency is depends upon the rotation....
Will a fuse work successfully connected in parallel?
Absolutely not. A fuse works by "monitoring" the current flowing in the circuit. Setting the fuse next to whatever it should be monitoring will do absolutely no good.
According to ohms law the current density is proportional to?
Current density is unrelated to Ohm's Law.
Is the gain same for same system in open loop and closed loop?
A: DEFINITELY NOT Open loop is defined as no feedback. any kind of negative feedback will reduce the gain
Relationship between resistance and capacitive reactance?
There is no physical relationship between resistance and capacitive reactance. But if someone tells you that the impedance of something: Z = 3 -4j, the real resistance is 3 and the reactive capacitance is -4.
How will be conduct test on transformer?
Short circuit test and open circuit test are widely used to test the efficiency of the transformer.
The points where circuits interconnect with other circuits is known as what?
The point where wires interconnect with other wires is known as a "junction".
In your panel the circuit breakers are connected to the buss, each circuit breaker feeds a different circuit. Different circuits are not connected together.
Capacitors are said to be connected together "in series" when they are effectively "daisy chained" together in a single line. The charging current ( iC ) flowing through the capacitors is THE SAME for all capacitors as it only has one path to follow.
Then, Capacitors in Series all have the same current flowing through them as iT = i1 = i2 = i3 etc.
Therefore each capacitor will store the same amount of electrical charge, Q on its plates regardless of its capacitance. This is because the charge stored by a plate of any one capacitor must have come from the plate of its adjacent capacitor. Therefore, capacitors connected together in series must have the same charge.
QT = Q1 = Q2 = Q3 , etc.
How is Ampacity calculations as per IEEE 738?
What is IEEE-738?
IEEE-738 is a widely used and accepted method of calculating the ampacity (thermal rating) of transmission conductors under specified weather conditions. Conductor parameters and major weather conditions are input into the method. Major weather conditions affecting rating include air temperature, wind speed/direction, and solar input, although there are some other minor effects. Both steady-state and short-duration ratings can be calculated.
IEEE-738 is based on both experimental data and theoretical equations. The full name of the standard is, "IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors". The standard may be purchased from IEEE (Institute of Electrical and Electronics Engineers, Inc.) at
How to Calculate a Thermal Rating
An equation to calculate conductor rating is developed by first recognizing that the total input heat (per unit length) to a conductor must equal the total output heat in the steady state. The conductor is heated by ohmic losses (I2R) and solar input, and it is cooled by convection and radiation.
The following equation and figure shows this main "heat balance":
Qsolar + I2R = Qconvection + Qradiation
where
- Qsolar is the heat input due to solar radiation, W/ft
- I2R is the heat input due to line current, W/ft (R is a function of conductor temperature)
- Qconvection is the heat output due to convection (a function of wind, air temp, conductor temp), W/ft
- Qradiation is the heat output due to radiation (a function of air temp and conductor temp), W/ft
Heating and Cooling of an Overhead Conductor
Now, the equation can be reworked to solve for current as a function of the weather conditions. The Qconvection, Qradiation, Qsolar, and R terms are all functions of weather conditions and of conductor temperature. If the weather conditions are measured and the conductor temperature is set to the maximum allowable conductor temperature,the calculated current is the rating current as shown in the following equation.
The capacitive reactance of a capacitor increase as?
The capacitive reactance of a capacitor increases as the frequency decreases.
How you using ref relay in transformer?
an REF relay (restricted earth fault) is used to provide ground fault protection for a transformer. Its' operation is limited by CTs starred towards the transformer (usually on the transformer bushings or in breakers used to isolate the transformer), so it will only operate for transformer related faults. Because of this, it can be set to operate very quickly.
How are N type semiconductors formed?
N-type semiconductors are a type of extrinsic semiconductor where the dopant atoms (donors) are capable of providing extra conduction electrons to the host material (e.g. phosphorusin silicon). This creates an excess of negative (n-type) electron charge carriers.
You would be hard pressed to accomplish this in a single stage amplifier. It's much easier with two.
For someone that hasn't done a whole lot of design, I would use two op amp stages to get there. the U741 op amp is a very common op amp, and is pretty cheap. For both stages you need to apply a +12 and -12 volt.
Here's the pin out for stage #1:
Tie 3 to your source
6 is your output. Connect a 100k ohm resistor from 6 to 2
Tie a 1k ohm resistor from 2 to ground.
And the second stage:
connect pin 6 of the first stage to 3 of the second
6 is your output. connect a 10k ohm resistor from 6 to 2
Tie a 1k ohm resistor from 2 to ground
Connect a 10 microFarad capacitor (12 volt minimim rated) from pin 6 to your output load. This will get rid of any DC offset, and the value does not necessarily have to be 10 microFarad, but the bigger, the better (usually).
This should have a pretty flat frequency response to ~3kHz. The first stage has a gain of ~100, the second has a gain of ~10. If you find the frequency response is poor, lowering the gain of the first stage and increasing the second will improve the frequency response. Replacing the 100k with a 50k will drop the first stage gain to ~50; replacing the 10k with a 22k will increase the second stage gain to ~20. This should have a frequency response that's fairly flat up to ~10kHz.
If you need an actual schematic, email me.
Is it superimposed load only live load?
Superimposed loads are the combination of all anticipated loads anticipated to be exerted on a structurally entity.
