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
A terminal potential difference is the potential difference appearing across the terminals of a voltage source, such as a battery or a generator, which varies according to the load supplied.
When the battery or generator is off load (i.e. no load is connected to it), the terminal potential difference is equal to the electromotive force of that battery or generator.
The terminal potential difference tends to decrease as the load current increases, due to a corresponding increase in the internal voltage drop of the battery or generator.
R for resistor, C for capacitor.
RC circuit is a circuit built with a resistor and a capacitor.
This circuit will have a typical pulse response that looks like exponential decaying and a typical resonance frequency.
What is an example of self-inductance?
self induction occurs in an Inductor itself. Self induction happens because of the flux change in the circuit due to varying current of the same circuit and not the current change of some other circuit thats why the term "self" is used
Engr. Saif Ali Solangi
What is the difference between 1sec and 3sec duration of short-circuit withstand capacity?
The difference between 1 second and 3 seconds is 2 seconds. In terms of short-circuit withstand capacity, it can mean the difference between no damage and damage occurring to the equipment and wiring. Heat rises extremely fast in a short-circuit situation, and you want your protective device to trip before damage is done.
What are the harmful effects of short-circuit fault on the power system?
A short circuit causes large amounts of power to flow. If left uninterrupted for long enough, this could cause system instability, and eventual collapse of the power grid (wide area blackouts).
Is a sump pump an open loop system?
A typical sump pump just sits there and does nothing until a sensor detects that sufficient water is present to turn on. If it just pumped forever it would be open loop. The fact that it also senses when the water has been pumped and stops makes it a closed loop system.
If you're referring to the water in the system, it is an open loop system, since the water is not held in the system.
How calculate ups battery backup time?
The UPS should be rated in Amps per Hour. Just divide that number by the current requirements of the device connected to the UPS. Say that the UPS is rated for 10 Ampere Hours and your device draws 2 amps. You could run the device for about 5 hours.
What can happen if the gas pressure in SF6 CB is dropped below the specified level?
SF6 is used to increase the dielectric strength of the gap in the circuit breaker. If the gas pressure is too low, the dielectric strength will be inadequate to break the voltage applied across the breaker contacts. This means electricity will continue to arc across the contacts when opened, causing the breaker to heat up and likely fail catastrophically (explode).
Most gas breakers have low gas alarms and trip contacts. If there is no way to bypass the breaker, a low gas trip contact can be used to open the breaker before the gas pressure gets too low to allow openning.
Why A synchronous motor is sometimes called a synchronous capacitor Explain?
A synchronous motor can operate as either a Generator or a Motor.
When a synchronous motor has current applied to the windings on its rotor and the stator is energized with say a 50hz line supply (with little or no physical load) then the exact amount of excitation provided by the rotor can determine whether the stator displays inductive or capacitive properties.
If the rotor is under excited (too Little rotor current) the Synchronous Motor will behave as an Inductor, however if the rotor is over excited then the Synchronous Motor will behave like a Capacitor.
Hope this helps
One ohm is a particular reading on the ohms scale of a multimeter. It corresponds, per Ohm's Law, to the resistance that a current of one ampere would cause a potential difference of one volt across. (Or one millampere and one millivolt, however it happens to scale.)
Do three 1m ohm resistors equal a 3m ohm resistor?
Only if you connect then in series.
RSERIES = Summation1toN (RN)
RPARALLEL = 1 / Summation1toN (1 / RN)
Are DC generators more expensive then AC generators?
DC generators require more time and material to make. Because of this, it will be cheaper to purchase an AC generator. DC generators are typically a better product as well, and you get what you pay for.
How do you calculate the electric field inside a conductor?
A spherical conductor with a radius of 14.0 cm and charge of 26.0 microcoulombs. Calculate the electric field at (a)r=10.0cm and (b)r=20.0cm and (c)r=14.0 from the center.
How do you convert percent impedance of transformer to impedance value?
The apparent impedance looking into a transformer from one side will not be the same as looking in it from the other, which is why percent impedance is used.
If you are looking from the high voltage winding (I'm labeling #1) to the low voltage winding (#2), you must scale the percent impedance as follows:
(% impedance) x (Winding #1 nominal voltage)^2 / (transformer base VA)
Are electric motors easier to maintain than gasoline motors?
Electric motors are generally easier and less expensive to maintain than gasoline motors for cars. Electric motors are more efficient and cleaner. There is a battery that needs to be replaced every three years, but there are no other spare parts.
tantalum,mica,paper,cermic
How 3 phase unbalanced current flow through neutral?
Kirchoff's Current Law states that the signed sum of the currents entering a node is zero. If the neutral point is the node, then, in a balanced system, hot matches the other two hots, resulting in no current through neutral. Any imbalance, either due to neutral to hot current flow that is not balanced by the other two neutral to hot current flows, or due to ground fault, will result in a current flow on neutral, so that the sum of zero is maintained.
When you think about this, remember that the law said "signed" and "entering". When you analyze a circuit, simply be consistent in your usage. For instance, in a balanced system, current entering the neutral node from one hot side is considered positive, and the current entering the neutral node from the other hot side is considered negative, i.e. it is leaving, not entering.
This gets more complicated in three phase power, because now you have to consider phase angle, but the concept is exactly the same...
If you are connected in wye, with a neutral, then the neutral conductor will have zero current on it only if the three phase hots have the same current on each. If you do vector analysis on this, adding up sin(x), sin(x+120), and sin(x+240), you get zero.
The same thing happens when you are delta connected, without a neutral, but then the imbalance occurs out in the distribution system, beyond the service transformers, because the distribution system is generally a wye system.
Ground fault will, of course, "change the rules", because you no longer have only four paths to that neutral point node. In fact, that is how ground fault current interrupters (GFCI's) work - they measure outbound current and compare it to inbound current - they must be equal and opposite, i.e. they cancel each other out - otherwise there is another path - a ground fault - and the device trips.
What is the firing angle of silicon controlled rectifier?
The SCR turns on based on gate voltage. The firing angle will depend on the point in the AC cycle where the gate voltage is where you want it, so the firing angle is a function of circuit design, not of the SCR.
How does a phase converter work?
A phase converter takes single phase electrical power and turns it into multiphase electrical power. It is very difficult to explain how exactly it does this, but it involves routing power to different capacitors and sequencing them to work together.
What happen if you reduced the number of devices on each parallel circuit?
The overall current will decrease by subtracting the current used by each device.
How capacitor is connected in a table fan?
The Capacitor with running winding is connected in parallel with main winding.
