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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 are instrumentation cables?
Instrumentation cables are not generic. Instrumentation cables are wires that allow for a signal to be put into one end and give the same signal at the other end without distortion. What that means is if the instrument has a resisitive sensing element the 'instrument cable' used would have a very low resistive value and protection from enviromential influence to the cable to not change the value. Instrumentation cable may also be used for powering a device - which once again if powered via regulated voltage you'll want to make sure the voltage given at one end is the same on the other end. Instrumentation cables are also used for high frequency measurements are made. These instrument cables will have a frequency limitation typically based on the length of cable used due to its capacitance.
There will be 20 amps flowing through the 5 ohm resistor. We could do some math and all to figure voltage drops and some other things, but let's cut to the chase and see what's happening. Based on what we know about series circuits and about parallel circuits, we can shred this in nothing flat. So let's. First, we're told 30 amps flows in the circuit. That's the total current, and it will be the current through the first 10 ohm resistor. It has to be. The the 30 amps "splits" to flow through the parallel network of the 10 ohm and 5 ohm resistors. That's 30 amps that has to "split" and some will go through the 10 ohm resistor and some will go through the 5 ohm resistor. With me? Sure. Now for the "trick" here. Since the 5 ohm resistor has only half the resistance of the 10 ohm resistor, twice as much current will flow through it as the 10 ohm resistor. Make sense? Yup. Let's finish this. Since there is twice as much current flowing in the 5 ohm resistor 'cause it's got half the resistance of the 10 ohm resistor, if we have "x" amount of current flowing in the 10 ohm resistor, then we'll have "2x" amps of current flowing in the 5 ohm resistor. That's "3x" amps total, and the "3x" amps equals 30 amps. See through it now? There will be 10 amps flowing through the 10 ohm resistor, and 20 amps flowing through the 5 ohm resistor. Piece of cake.
What is the difference between power transformers and pulse transformers?
A 'voltage transformer', together with a 'current transformer', belong to a class of transformers called 'instrument transformers', whose purpose is to enable high voltages and currents to be safely measured by reducing their values to lower levels, while electrically-isolating these high voltages/currents from the measuring instruments. These transformers are also used to provide input to protective relays.
A 'power transformer' is a transformer used in the electricity transmission and primary distribution systems, whose function is to either step up generated voltages (11 - 25 kV in the UK) to transmission levels (400 kV in the UK), or to step down these high voltages at 'load centres', such as towns and cities.
Which winding has the higher resistance start or run in single phase motors?
start winding is thicker with less number of winding whereas run winding is less thicker than start winding but with more number of winding. As we know inductance depends upon numbers of turns of winding so run winding will have more inductance.
What is 120 AC volts equal to in DC volts?
There is no direct comparison but this is one way to look at it...
120v ac, if measured correctly, is the effective voltage of the circuit and is basically the same as 120v dc for items that can run on either. Not many things besides purely resistive circuits, such as incandescent lights, can run on either. Effective voltage is not the same as average voltage, another way of measuring volts.
Alternative AnswerUnless otherwise stated, an a.c. current is alwaysexpressed as a root-mean-square (r.m.s.) value. This is the value of a.c. current that will do exactly the same amount of work as a d.c. current of the same value. In other words, 5 A (for example) a.c. is exactlyequivalent to 5 A d.c. Since voltage is proportional to current, we can say the same thing about a.c. voltages. So, 120 V a.c. is exactly equivalent to 120 V d.c.
What is Full load current for 40 HP star delta motor?
What is the continuous current of 10HP star delta motor
What is the effect of dielectric on the capacitance of a capacitor?
Any variation of the charge within a p-n diode with an applied voltage variation yields a capacitance wich must be added to the circuit model of a p-n diode. The capacitance associated with the charge variation in the depletion layer is called the junction capacitance, while the capacitance associated with the excess carriers in the quasi-neutral region is called the diffusion capacitance. Both types of capacitances are non-linear so that we will derive the small-signal capacitance in each case. We will find that the junction capacitance dominates for reverse-biased diodes, while the diffusion capacitance dominates in strongly forward-biased diodes. The total capacitance is the sum of both.
A diode blocks current flowing in one direction, and passes a current going into the other direction (with a little potential energy loss).
DC is a current flowing into one direction all the time. therefore if you put a diode in a dc circuit it will either always block or always let it pass (provided a certain amount of supply voltage).
if you have an ac circuit the current alternates (ac=alternating current) most of the cases the current flows half of the time in one direction and half of the time into the other direction. so you will have both cases 50% blocking 50% passing through.
so if you put an LED into an ac circuit, no matter what way you put it in you will always see light.
How do you connect bulb in 3 phase power?
by using star connection
AnswerIt depends on the type of three-phase supply. If it's a three-wire system, then you can connect the lamp between any pair of line conductors. If it's a four-wire system, then you can connect the lamp either between any pair of line conductors or between any one line conductor and the neutral conductor. Of course, the voltage rating of the lamp must match the line-to-line voltage or the line-to-neutral voltage.
What is ceiling voltage in exciter?
ceiling voltage is the maximum field voltage that the exciter can withstand before going into unstability
A: If you are lucky a fuse blow or a circuit breaker opens up. If not a fire maybe started in the walls where is hard to see and put it out. In the USA the outlets are implemented to be used with a 15 amperes total. By drawing more current continuously the wiring get hot because of the current passing to the load if sustained for too long a fire may start. It is preferable to short out the outlet because that will insure a fuse blow or a circuit breaker open up continuous overload is very dangerous
What is the difference between an arc fault breaker and and a ground fault breaker?
A ground fault circuit interrupter is as its name implies, a device (circuit breaker or special receptacle) which interrupts (shuts down) a circuit when it detects a ground fault (current flowing to ground). When a small amount of current (4 to 6 milliamperes) is detected flowing to ground by the electronics within the device it trips so that no more current can flow, thereby possibly saving your life. Example: you are listening to the radio while having a bath and it falls into the tub--- the circuit will turn off before you can be harmed. GFCI's as they are commonly called are required by the Electrical Code to be installed in bathrooms, kitchens where the receptacle is within one meter of the sink, any outdoor location (rain and snow) and any other wet or damp locations. (refer to code book) An Arc Fault Circuit Interrupter is a device( I've seem breakers but am unsure whether there is a special AFCI receptacle) which shuts off a circuit when it detects an arcing condition in the circuit. An example of arcing would be when you pull the plug out of a wall receptacle when the device plugged in is under load (turned on) and you see a little (sometimes big depending on the size of the load) bluish or yellowish flash or "arc". Receptacles on AFCI circuit breakers are required by the electrical code to be installed in bedrooms. It has something to do with the flammability of linens and blankets I believe, but here again for detailed info please consult the official Electrical Code book for your location.
What is a multi ratio transformer?
A multi ratio CT is just that, it's a CT that has multiple secondary taps. An example is a 1200/5, 5 tap CT, which can be set to many ratios between 100/5 and 1200/5.
Which power factor is advantage lagging or leading and why?
A lagging power factor is caused by inductive reactance, which is composed of resistance and inductance -- and the resistance component lowers the supply volts. A leading power factor provides capacitive reactance that actually helps improve source voltage -- this helps motor loads run cooler.
What is the Difference between half wave and full wave rectification?
A half wave rectifier is a special case of a clipper. In half wave rectification, either the positive or negative half of the AC wave is passed easily, while the other half is blocked, depending on the polarity of the rectifier. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. Half-wave rectification can be achieved with a single diode in a one phase supply.
In half wave rectification, either the positive or negative half of the AC wave is passed, while the other half is blocked. Because only one half of the input waveform reaches the output, it is very inefficient if used for power transfer. Half-wave rectification can be achieved with a single diode in a one phase supply, or with three diodes in a three-phase supply.
in half wave rectifier only one diode is there. The diode will be forward biased in the positive half cycle and reverse biased in the negative half cycle. So the out put will be available only during the positive half cycle and the out put will be unidirectional.
Full-wave rectificationA full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Full-wave rectification converts both polarities of the input waveform to DC (direct current), and is more efficient. However, in a circuit with a non-center tapped transformer, four diodes are required instead of the one needed for half-wave rectification. (See semiconductors, diode). Four rectifiers arranged this way are called a diode bridge or bridge rectifier:For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back (i.e. anodes-to-anode or cathode-to-cathode) form a full-wave rectifier (in this case, the voltage is half of that for the non-tapped bridge circuit above, and the diagram voltages are not to scale).
In a full wave rectifier during each half cycle one of the diode will be forward biased and output will be available across the load resistor. So we get continuous dc output throughout the cycle.
- no.. of diods 1 in half wave rect....
What is the formula for fire load?
Fire load = M x C kilojoules / metre square
A
Where:-
M = mass of combustible materials in the compartment or storey (kilograms)
C = calorific value of the materials (kilojoules / kilogram)
A = floor area (m2)
I'm not sure that will appear correctly.... you multiply MxC and divide by A
What is the instrument called that can change electrical voltage?
Electrical voltage can be changed by a transformer.
What is the color code for a 8 ohm resistor?
Green - Black - Red, but this is not a standard value. You probably want a 5.1K resistor, and that is Green, Brown, Red
Why are fuses used for protection of resistive loads?
Fuses actually have a lower resistance that the wire or carrier that is carrying current to and from the fuse. The purpose of a fuse is so that it will burn out before the carrier burns out. When a fuse burns out it breaks the current and therefore no more electricity can pass through it until the fuse is replaced. You gauge the fuse for a little more current than you normally have traveling through the wire. If a power surge of electricity comes through the wire the fuse will burn out instead of damaging the electrical device that is plugged into or wired into the carrier.
Why to ground star side of transformer?
Star connections allow for grounding of the system, which is required for single phase loads, and beneficial for three phase for a number of different reasons. Because it can be grounded, it can also supply ground current to operate protective devices. There may be other more specific reasons applicable to what exactly you are looking at (special case application? voltage level? surrounding system? etc.).
Does more current flow into a light bulb than out of it?
No. Although there is a voltage drop across the filament of an incandescent light bulb, the amount of current flowing out is identical to what flows in: current in = current out. That is an important fact to always keep in mind when solving simple electrical circuits: the sum of the currents flowing into a node equals the sum of the currents flowing out of it.
How a gas insulated substation works?
This seems like a question from an electrical course, and is probably best answered by your course materials.
It's your test question, not ours, and there won't always be someone to ask for the answer. Earn your diploma.
How could a fuse be triggered?
Fuses are triggered, or more correctly blown, when the current through them exceeds their preset limit. A short circuit would be one example, where you might see several hundred amperes in a 15 ampere circuit, but only for a short time, as the fuse would blow nearly instantly. An overload would be another example, where you might see 25 or 30 amperes in a 15 ampere circuit. It might take some time, seconds or minutes, depending on the overload time characteristics of the fuse because, in that case, the fuse is designed to allow short time overloads to allow motor startup.
we use to connect elcb using hands. with help of skrewdriver
Why is a rotating field system used in preference toa stationary field?
If you are asking why most a.c. generators (alternators) use a rotating field, rather than a rotating armature, then the answer is that a rotating armature would require slip rings to carry huge currents and be insulated for high voltages, which is not practicable.
